Liquid discharging apparatus and circuit substrate

ABSTRACT

A liquid discharging apparatus includes a print head that has a driving element and discharges a liquid, a drive signal generation circuit that generates the drive signal based on a drive signal generation control signal for controlling generation of the drive signal, and a drive circuit substrate on which the drive signal generation circuit is provided. The drive circuit substrate has an input connector that inputs the drive signal generation control signal into the drive circuit substrate and an output connector that outputs the drive signal from the drive circuit substrate. A distance between the input connector and the output connector is shorter than a distance between the drive signal generation circuit and the input connector. The distance between the input connector and the output connector is shorter than a distance between the drive signal generation circuit and the output connector.

BACKGROUND 1. Technical Field

The present invention relates to a liquid discharging apparatus and acircuit substrate.

2. Related Art

An apparatus using a piezoelectric element is known as a liquiddischarging apparatus such as an ink jet printer that discharges inksand prints an image or characters. The piezoelectric element is providedso as to correspond to each of a plurality of nozzles in a head (printhead), and each of the nozzles is driven in accordance with a drivesignal. As a consequence, a predetermined amount of ink (liquid) isdischarged at a predetermined timing from the nozzles, and thereby dotsare formed. Since the piezoelectric element is a capacitive load like acapacitor from an electrical perspective, it is necessary to supply asufficient amount of current in order to operate the piezoelectricelement of each nozzle. For this reason, a configuration where a drivecircuit supplies a drive signal amplified by an amplification circuitand the piezoelectric element is driven is adopted in the liquiddischarging apparatus described above.

The layout of a circuit substrate on which a plurality of drive circuitsthat generate drive signals for driving a head are mounted is disclosedin JP-A-2010-221500.

In a liquid discharging apparatus such as an ink jet printer, the numberof drive nozzles increases in accordance with an increase in printingspeed and an increase in image quality, and the amount of heat generatedin a drive circuit increases as well. For this reason, in a case where aplurality of drive circuits for generating drive signals are mounted ona circuit substrate as in the circuit substrate disclosed inJP-A-2010-221500, there is a possibility that the amount of heatgenerated in the circuit substrate further increases. In addition, sincethe heat generated in the drive circuit has an effect on not only thedrive circuit itself but also a peripheral configuration, there is apossibility that discharge characteristics and the product life of aliquid discharging apparatus are also affected. For this reason, variouscooling component are used in order to enhance cooling efficiency of thecircuit substrate on which the drive circuit is mounted.

However, the layout of the circuit substrate for the cooling componentsto efficiently cool is not disclosed and there is a possibility thatrestriction of disposing the cooling components is generated due to thelayout of the circuit substrate.

SUMMARY

An advantage of some aspects of the invention is to provide a liquiddischarging apparatus and a circuit substrate, in which restriction ofdisposing cooling components is reduced and a high degree of freedom ofdisposing the cooling components is ensured on the circuit substrate onwhich a drive circuit is mounted.

The invention can be realized in the following aspects or applicationexamples.

APPLICATION EXAMPLE 1

According to this application example, there is provided a liquiddischarging apparatus including a print head that has a driving elementand discharges a liquid when a drive signal is applied and the drivingelement is driven, a drive signal generation circuit that generates thedrive signal based on a drive signal generation control signal forcontrolling generation of the drive signal, and a drive circuitsubstrate on which the drive signal generation circuit is provided. Thedrive circuit substrate has an input connector that inputs the drivesignal generation control signal into the drive circuit substrate and anoutput connector that outputs the drive signal from the drive circuitsubstrate. A distance between the input connector and the outputconnector is shorter than a distance between the drive signal generationcircuit and the input connector. The distance between the inputconnector and the output connector is shorter than a distance betweenthe drive signal generation circuit and the output connector.

The driving element may be, for example, a piezoelectric element, or maybe a heater element.

In the liquid discharging apparatus according to this applicationexample, the distance between the input connector and the outputconnector is shorter than the distance between both of the inputconnector and the output connector and the drive signal generationcircuit, on the drive circuit substrate that generates a drive signal.That is, a region where the input connector and the output connector aredisposed and a region where the drive signal generation circuitgenerating heat is disposed are disposed in different regions on thedrive circuit substrate. Accordingly, it is possible to dispose acooling component for cooling the heat generating drive signalgeneration circuit without being restricted by any of the inputconnector which inputs a signal into the drive signal generation circuitand the output connector which outputs a signal from the drive signalgeneration circuit. Therefore, it is possible to provide the liquiddischarging apparatus, in which restriction of disposing the coolingcomponent is reduced and a high degree of freedom of disposing thecooling component is ensured.

It is possible to optimally dispose the cooling component on the drivesignal generation circuit, and it is possible to efficiently cool a heatgenerating component. It is possible to reduce an effect of heatgenerated in the drive signal generation circuit on a peripheralconfiguration. Therefore, an effect on the discharge characteristics andthe product life of the liquid discharging apparatus can be reduced.

APPLICATION EXAMPLE 2

In the liquid discharging apparatus according to the applicationexample, a fan may be further included. The fan may be provided at aposition intersecting a direction where a plane of the drive circuitsubstrate extends. A distance between the fan and the drive signalgeneration circuit may be shorter than a distance between the fan andthe input connector. The distance between the fan and the drive signalgeneration circuit may be shorter than a distance between the fan andthe output connector.

In the liquid discharging apparatus according to the applicationexample, the fan is included as a cooling device, and the fan isprovided on a side of the drive circuit substrate where the drive signalgeneration circuit is provided. Accordingly, it is possible for the fanto efficiently cool the drive signal generation circuit without beingaffected by the disposition of the input connector and the outputconnector.

In the liquid discharging apparatus according to the applicationexample, the fan is provided so as to intersect the direction where theplane of the drive circuit substrate extends. That is, it is possible toselectively cool both of or one of the front side and the back side ofthe drive circuit substrate. Therefore, it is possible to efficientlycool the drive circuit substrate.

APPLICATION EXAMPLE 3

In the liquid discharging apparatus according to the applicationexample, a drive circuit accommodating unit that accommodates the drivecircuit substrate and has an opening may be further included. Theopening may be provided at a position intersecting a direction where aplane of the drive circuit substrate extends. A distance between theopening and the drive signal generation circuit may be shorter than adistance between the opening and the input connector. The distancebetween the opening and the drive signal generation circuit may beshorter than a distance between the opening and the output connector.

In the liquid discharging apparatus according to the applicationexample, the drive circuit substrate may be accommodated in the casehaving the opening. The sticking of a liquid discharged from the printhead to the drive circuit substrate can be reduced by the caseaccommodating the drive circuit substrate. Therefore, on the drivecircuit substrate, the occurrence of a defect such as an insulationfailure caused by a liquid discharged from the print head is reduced.

In the liquid discharging apparatus according to the applicationexample, the opening of the case is provided on a drive signalgeneration circuit side so as to intersect the direction where the planeof the drive circuit substrate extends. That is, heat generated in thedrive signal generation circuit is unlikely to stay in the case and isdischarged to the outside of the case from the opening. Therefore, it ispossible to efficiently cool the drive signal generation circuit.

APPLICATION EXAMPLE 4

In the liquid discharging apparatus according to the applicationexample, a radiator may be further included. The radiator may beprovided on a surface of the drive circuit substrate, which is differentfrom a surface on which the drive signal generation circuit is provided.In planar view of the drive circuit substrate, the drive signalgeneration circuit and the radiator may be provided at positions whereat least a part of the drive signal generation circuit and a part of theradiator overlap each other.

In the liquid discharging apparatus according to the applicationexample, the radiator is included as a cooling device and the radiatoris provided on the surface of the drive circuit substrate, which isdifferent from the surface of the drive signal generation circuit, andis provided so as to overlap the drive signal generation circuit. Thatis, it is possible for the radiator to dissipate heat generated in thedrive signal generation circuit from the surface of the drive circuitsubstrate on which the drive signal generation circuit is not provided.Accordingly, it is possible to dissipate heat generated in the drivesignal generation circuit.

APPLICATION EXAMPLE 5

In the liquid discharging apparatus according to the applicationexample, the drive signal generation control signal may be a digitalsignal, the drive signal generation circuit may generate an underlyingdrive signal, which is an underlying analog signal of the drive signal,based on the drive signal generation control signal, and the drivesignal generation circuit may power-amplify the underlying drive signalto generate the drive signal.

In the liquid discharging apparatus according to the applicationexample, the drive signal generation control signal input into the drivesignal generation circuit is input as a digital signal. That is, thedrive signal generation control signal, which is an underlying signal ofthe drive signal, is unlikely to receive an effect of external noises.Thus, the drive signal generation control signal is accurately inputinto the drive signal generation circuit. Therefore, there is apossibility that the accuracy of the drive signal output from the drivesignal generation circuit improves.

In the liquid discharging apparatus according to the applicationexample, the drive signal generation control signal input into the drivesignal generation circuit may be input as a differential signal.Accordingly, it is possible to reduce an effect of external noises (inparticular, common mode noises) on the drive signal generation controlsignal input into the drive signal generation circuit. Thus, the drivesignal generation control signal is accurately input into the drivesignal generation circuit. Therefore, there is a possibility that theaccuracy of the drive signal output from the drive signal generationcircuit improves.

APPLICATION EXAMPLE 6

According to this application example, there is provided a circuitsubstrate including a drive signal generation circuit that generates adrive signal for driving a driving element based on a drive signalgeneration control signal, an input connector that inputs the drivesignal generation control signal, and an output connector that outputsthe drive signal. A distance between the input connector and the outputconnector is shorter than a distance between the drive signal generationcircuit and the input connector. The distance between the inputconnector and the output connector is shorter than a distance betweenthe drive signal generation circuit and the output connector.

In the circuit substrate according to this application example, thedistance between the input connector and the output connector is shorterthan the distance between both of the input connector and the outputconnector and the drive signal generation circuit, on the drive circuitsubstrate that generates a drive signal. That is, the region where theinput connector and the output connector are disposed and the regionwhere the drive signal generation circuit generating heat is disposedare disposed in different regions. Accordingly, it is possible todispose a cooling component for cooling the heat generating drive signalgeneration circuit without being restricted by any of the inputconnector which inputs a signal into the drive signal generation circuitand the output connector which outputs a signal from the drive signalgeneration circuit. Therefore, it is possible to provide the liquiddischarging apparatus, in which restriction of disposing the coolingcomponent is reduced and a high degree of freedom of disposing thecooling component is ensured.

By the cooling component of the drive signal generation circuitefficiently performing cooling, it is possible to reduce an effect ofheat generated in the drive signal generation circuit on a peripheralconfiguration and an effect on discharge characteristics and the productlife of the liquid discharging apparatus can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic view illustrating an appearance of a liquiddischarging apparatus.

FIG. 2 is a block diagram showing an electrical configuration of theliquid discharging apparatus.

FIG. 3 is a view illustrating a schematic configuration corresponding toone discharging unit of a head.

FIG. 4 is a view illustrating an example of array of nozzles.

FIG. 5 is a view for illustrating basic resolution of image formation bynozzle array.

FIG. 6 is a diagram showing waveforms of drive signals.

FIG. 7 is a diagram showing the waveforms of the drive signals.

FIG. 8 is a diagram showing a circuit configuration of a drive circuit.

FIG. 9 is a diagram for illustrating operation of the drive circuit.

FIG. 10 is a diagram showing a configuration of a selection controlunit.

FIG. 11 is a diagram showing contents of decoding by a decoder.

FIG. 12 is a diagram showing a configuration of a selecting unitcorresponding to one piezoelectric element (nozzle).

FIG. 13 is a diagram for illustrating operation of the selection controlunit and operation of the selecting unit.

FIG. 14 is a diagram showing an internal configuration of a head unitwhen seen in a main scanning direction in a first embodiment.

FIG. 15 is a diagram showing the internal configuration of the head unitwhen seen in the main scanning direction in the first embodiment.

FIG. 16 is an exploded perspective view illustrating a configuration ofa drive unit in the first embodiment.

FIG. 17 is a schematic view illustrating layout of a drive circuitsubstrate in the first embodiment.

FIG. 18 is a schematic view illustrating layout of a drive circuitsubstrate in a second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, suitable embodiments of the invention will be described indetail with reference to the drawings. The referred drawings are for theconvenience of description. The embodiments to be described below do notwrongfully limit the content of the invention described in the scope ofclaims. Not all configurations described below are essentialconfiguration requirements.

1 First Embodiment

1.1 Outline of Liquid Discharging Apparatus

A printing apparatus, which is an example of a liquid dischargingapparatus according to a first embodiment, is an ink jet printer thatforms ink dot groups onto a printing medium, such as paper, bydischarging inks according to image data supplied from an external hostcomputer and thereby prints an image (including characters and figures)corresponding to the image data.

In addition to the printing apparatus such as a printer, a colormaterial discharging apparatus used in manufacturing color filters, suchas a liquid crystal display, an electrode material discharging apparatusused in forming electrodes such as an organic EL display and a fieldemission display (FED), a bioorganic material discharging apparatus usedin manufacturing biochips, a three-dimensional modelling apparatus(so-called 3D printer), and a textile printing apparatus can be given asexamples of the liquid discharging apparatus.

FIG. 1 is a schematic view illustrating an appearance of a liquiddischarging apparatus 1. As illustrated in FIG. 1, the liquiddischarging apparatus 1 is a serial scan type (serial printing type)large format printer, and includes a main body 2 and a support stand 3that supports the main body 2. The large format printer is, for example,a printer that corresponds to the size of paper having an A3 short sidewidth (297 mm×420 mm) or longer, which is a printable size of a printingmedium, and the large format printer in the first embodiment is aso-called large format printer (LFP) of which maximum printable size ofa printing medium P is approximately 70 inches. In the first embodiment,in FIG. 1, a moving direction of a carriage 24 of the liquid dischargingapparatus 1 will be referred to as a main scanning direction X, atransporting direction of the printing medium P of the liquiddischarging apparatus 1 will be referred to as a sub-scanning directionY, and a vertical direction of the liquid discharging apparatus 1 willbe referred to as a vertical direction Z. Although the main scanningdirection X, the sub-scanning direction Y, and the vertical direction Zare illustrated as three axes of X, Y, and Z, which are orthogonal toeach other, in the drawings, a disposition relationship of each unit isnot necessarily limited to being orthogonal to each other.

As illustrated in FIG. 1, the main body 2 includes a supplying unit 4that supplies the printing medium (rolled paper) P, a printing unit 5that discharges ink droplets onto the printing medium P to performprinting onto the printing medium P, a sending-out unit 6 that sends theprinting medium P printed by the printing unit 5 out from the main body2, an operation unit 7 that performs operation of execution and stop ofprinting, and an ink storing unit 8 that stores an ink (liquid) to bedischarged. Although not illustrated, a USB port and a power supply portare provided in the rear surface of the liquid discharging apparatus 1.That is, the liquid discharging apparatus 1 is configured so as to beconnectable to a computer via a USB port.

The printing unit 5 is configured so as to include a head unit 20, acarriage guide shaft 32, and an ink tube 9.

The head unit 20 is configured so as to include the carriage 24 and ahead 21 that is mounted on the carriage 24 so as to oppose the printingmedium (rolled paper) P. The head 21 is a liquid ejecting head fordischarging ink droplets (liquid droplets) from multiple nozzles. Inaddition, the carriage 24 is supported by the carriage guide shaft 32and moves (reciprocates) in the main scanning direction X. At this time,the printing medium P is transported in the sub-scanning direction Y.That is, the liquid discharging apparatus 1 in the first embodimentperforms serial printing, in which the head unit 20, including thecarriage 24 on which the head 21 discharging ink droplets (liquid) ismounted, moves (reciprocates) and prints in the main scanning directionX.

A plurality of ink cartridges 22 are attached to the ink storing unit 8,and each of the ink cartridges 22 is filled with an ink having acorresponding color. Although the four ink cartridges 22 correspondingto four colors such as cyan (C), magenta (M), yellow (Y), and black (B)are illustrated in FIG. 1, the ink cartridges 22 are not limited to thisconfiguration. For example, four or more ink cartridges 22 may beincluded, or the ink cartridges 22 for different colors such as gray,green, and violet may be configured to be included. An ink accommodatedin each of the ink cartridges 22 is supplied to the head 21 via the inktube 9.

1.2 Electrical Configuration of Liquid Discharging Apparatus

FIG. 2 is a block diagram showing an electrical configuration of theliquid discharging apparatus 1 of the first embodiment.

As shown in FIG. 2, the liquid discharging apparatus 1 includes acontrol unit 10 that controls discharging of a liquid, the head unit 20that has discharging units 600 which discharge liquids, a drive unit 30that generates a drive signal, and a plurality of cables 19 connectingthese configurations together. Although the liquid discharging apparatus1 may be configured so as to include a plurality of head units 20, onehead unit 20 represents the plurality of head units in FIG. 2.

The control unit 10 is configured so as to include a control signalgenerating unit 100, a control signal converting unit 110, a controlsignal transmitting unit 120, and a drive data transmitting unit 140.

The control signal generating unit 100 outputs various types of controlsignals for controlling each unit when various types of signals, such asimage data, are supplied from the host computer. Specifically, thecontrol signal generating unit 100 generates a control signal forcontrolling a carriage moving mechanism 41 and a control signal forcontrolling a paper transporting mechanism 42. The carriage movingmechanism 41 moves (reciprocates) the carriage 24 in the main scanningdirection X, for example, by controlling the rotation of a motor formoving the carriage 24. In addition, the paper transporting mechanism 42supports, for example, the continuous printing medium P, which is woundin a roll shape, so as to be rotatable, and transports the printingmedium P by rotation. That is, by the carriage moving mechanism 41 andthe paper transporting mechanism 42 operating based on control signalsfrom the control signal generating unit 100, it is possible to performprinting at a predetermined position on the printing medium P.

The control signal generating unit 100 generates a control signal forcausing a maintenance mechanism 80 to execute maintenance processing forreturning ink discharge states of the discharging units 600 to normal.Based on the control signal from the control signal generating unit 100,the maintenance mechanism 80 performs cleaning processing (pumpingprocessing), in which thickened inks and bubbles in the dischargingunits 600 are suctioned by a tube pump (not illustrated), and wipingprocessing, in which foreign substances, such as paper dust stuck aroundnozzles of the discharging units 600, are wiped off by a wiper, asmaintenance processing.

The control signal generating unit 100 generates an original clocksignal sSck, an original print data signal sSI, an original latch signalsLAT, and an original change signal sCH, based on various types ofsignals from the host computer, as a plurality of types of originalcontrol signals for controlling the discharging of liquids from thedischarging units 600, and outputs the signals to the control signalconverting unit 110 in a parallel format. In the plurality of types oforiginal control signals, some of the signals may not be included, orother signals may be included.

In addition, the control signal generating unit 100 generates originaldrive data pieces sdA and sdB, which are data pieces indicating drivesignals for driving the discharging units 600 included in the head unit20, based on various types of signals from the host computer, andoutputs the data pieces to the drive data transmitting unit 140 in aparallel format. For example, the original drive data pieces sdA and sdBmay be digital data pieces obtained by converting the waveforms (drivewaveforms) of drive signals from analog to digital, may be digital datapieces that define a corresponding relationship between a length and aslope of each section where a slope is constant in a drive waveform, ormay be digital data pieces in which one of a plurality of types of drivewaveforms stored in a memory unit (not illustrated) is selected.

The control signal converting unit 110 converts (serializes) theplurality of types of original control signals (the original clocksignal sSck, the original print data signal sSI, the original latchsignal SLAT, and the original change signal sCH) output from the controlsignal generating unit 100 to a serial control signal in one serialformat, and outputs the signal to the control signal transmitting unit120. The control signal converting unit 110 generates a clock signal fortransmission used in high-speed serial data transmission via the cable19, and incorporates the clock signal for transmission into the serialcontrol signal along with the plurality of types of original controlsignals.

The control signal transmitting unit 120 converts the serial controlsignal output from the control signal converting unit 110 to originalcontrol differential signals dCS, and transmits the signals to the headunit 20 via the cable 19. The cable 19 through which the originalcontrol differential signals dCS output from the control signaltransmitting unit 120 are transmitted will be referred to as an FFC 191.

For example, the control signal transmitting unit 120 converts theserial control signal to differential signals in a low voltagedifferential signaling (LVDS) transmission mode and outputs the signalsto the head unit 20. Since the amplitudes of the differential signals inthe LVDS transmission mode are approximately 350 mV, high-speed datatransmission can be realized. The control signal transmitting unit 120may transmit differential signals in various types of high-speedtransmission modes other than LVDS, such as low voltage positive emittercoupled logic (LVPECL) and current mode logic (CML), to the head unit20. The control signal transmitting unit 120 may independently transmita clock signal for transmission to the head unit 20 without the controlsignal converting unit 110 incorporating the clock signal fortransmission into a serial control signal.

The drive data transmitting unit 140 converts the original drive datapieces sdA and sdB output from the control signal generating unit 100 tooriginal drive differential signals dDSA and dDSB respectively (examplesof a “drive signal generation control signal”), which are digitalsignals in a serial format, and transmits the data to the drive unit 30via the cable 19. The cable 19 through which the original drivedifferential signals dDSA and dDSB output from the drive datatransmitting unit 140 included in the control unit 10 are transmittedwill be referred to as an FFC 192.

For example, the original drive differential signals dDSA and dDSBoutput from the drive data transmitting unit 140 are digital signals.Specifically, the drive data transmitting unit 140 may convert each ofthe original drive data pieces sdA and sdB to a differential signal in ahigh-speed transmission mode such as LVDS and transmit the signals tothe head unit 20. The drive data transmitting unit 140 may serialize theoriginal drive data pieces sdA and sdB to one serial signal in a serialformat, and convert the serial signal to the original drive differentialsignals dDSA and dDSB to transmit the signal to the head unit 20. Thedrive data transmitting unit 140 may incorporate a clock signal fortransmission used in high-speed serial data transmission into adifferential signal, or may independently transmit the clock signal fortransmission to the head unit 20.

The drive unit 30 is configured so as to include a drive data receivingunit 330 and drive circuits 50-a and 50-b.

The drive data receiving unit 330 receives the original drivedifferential signals dDSA and dDSB transmitted from the control unit 10,and outputs drive data pieces dA and dB, which are data piecesindicating drive signals for driving the discharging units 600 providedin the head unit 20. Specifically, the drive data receiving unit 330differential-amplifies the received original drive differential signalsdDSA and dDSB, restores a clock signal for transmission incorporated inthe differential-amplified signal, and outputs the drive data pieces dAand dB in a parallel format by restoring the original drive data piecessdA and sdB included in the differential-amplified signal based on theclock signal for transmission.

The drive circuits 50-a and 50-b (examples of a “drive signal generationcircuit”) generate drive signals COM-A and COM-B for driving each of thedischarging units 600 provided in the head unit 20 based on the drivedata pieces dA and dB output from the drive data receiving unit 330.

For example, if the drive data pieces dA and dB are digital data piecesobtained by converting the waveforms of the drive signals COM-A andCOM-B, respectively, from analog to digital, the drive circuits 50-a and50-b generate analog signals obtained by converting the drive datapieces dA and dB, respectively, from digital to analog, and after then,amplify the signals with a class D amplifier to generate the drivesignals COM-A and COM-B.

For example, if each of the drive data pieces dA and dB is digital datathat defines a corresponding relationship between a length and a slopeof each section of which slope is constant in each of the waveforms ofthe drive signals COM-A and COM-B, each of the drive circuits 50-a and50-b generates an analog signal that satisfies the correspondingrelationship between a length and a slop of each section defined by eachof the drive data pieces dA and dB and amplifies the signal with a classD amplifier to generate the drive signals COM-A and COM-B.

For example, if each of the drive data pieces dA and dB is digital datain which one of a plurality of types of drive waveforms stored in thememory unit (not illustrated) is selected, each of the drive circuits50-a and 50-b generates an analog signal selected in each of the readdrive data pieces dA and dB and amplifies the signal with a class Damplifier to generate the drive signals COM-A and COM-B.

As described above, the drive data pieces dA and dB are data piecesdefining the waveforms of the drive signals COM-A and COM-B,respectively. The drive signals COM-A and COM-B generated by the drivecircuits 50-a and 50-b are transmitted to the head unit 20 via the cable19. The cable 19 through which the drive signals COM-A and COM-B aretransmitted to the head unit 20 will be referred to as an FFC 194. Thedrive circuits 50-a and 50-b are different only in terms of data to beinput and a drive signal to be output, and may have the same circuitconfiguration. Although the plurality of drive circuits 50-a and 50-bmay be included in the drive unit 30, a pair of drive circuits 50-a and50-b represents the plurality of drive circuits in FIG. 2.

The head unit 20 has a control signal receiving unit 310, a controlsignal restoring unit 320, a selection control unit 210, a plurality ofselecting units 230, and the head 21. Although only one head 21 is shownin FIG. 2, the head unit 20 of the first embodiment may include aplurality of heads 21.

The control signal receiving unit 310 receives the original controldifferential signals dCS transmitted from the control unit 10 via theFFC 191 and converts the received original control differential signalsdCS to a serial control signal to output to the control signal restoringunit 320. Specifically, the control signal receiving unit 310 mayreceive differential signals in the LVDS transmission mode anddifferential-amplify the differential signals to convert to a serialcontrol signal.

The control signal restoring unit 320 generates a plurality of types ofcontrol signals (a clock signal Sck, a print data signal SI, a latchsignal LAT, and a change signal CH) for controlling the discharging ofliquids from the discharging units 600 based on the serial controlsignal converted by the control signal receiving unit 310. Specifically,the control signal restoring unit 320 restores the clock signal fortransmission incorporated in the serial control signal output from thecontrol signal receiving unit 310, and restores (deserializes) theplurality of types of original control signals (the original clocksignal sSck, the original print data signal sSI, the original latchsignal sLAT, and the original change signal sCH) included in the serialcontrol signal based on the clock signal for transmission to generatethe plurality of types of control signals (the clock signal Sck, theprint data signal SI, the latch signal LAT, and the change signal CH) ina parallel format.

The selection control unit 210 instructs each of the selecting units 230of which signal should be selected from the drive signals COM-A andCOM-B (or neither of the signals should be selected) by mean of theplurality of types of control signals (the clock signal Sck, the printdata signal SI, the latch signal LAT, and the change signal CH).

Each of the selecting units 230 selects from the drive signals COM-A andCOM-B in accordance with an instruction from the selection control unit210, and supplies the signal to one end of each of the piezoelectricelements 60 included in the head 21 (an example of a “print head”) as adrive signal Vout. A voltage VBS is commonly applied to the other end ofeach of the piezoelectric elements 60.

The piezoelectric elements 60 (examples of a “driving element”) aredisplaced when drive signals are applied thereto. Each of thepiezoelectric elements 60 is provided so as to correspond to each of theplurality of discharging units 600 in the head 21. The piezoelectricelements 60 are displaced according to a difference between the drivesignal Vout and the voltage VBS selected by the selecting units 230 todischarge inks.

1.3 Configuration of Printing Head

1.3.1 Configuration of Discharging Unit

Herein, a configuration for discharging inks by driving of thepiezoelectric elements 60 will be briefly described.

FIG. 3 is a view illustrating a schematic configuration corresponding toone discharging unit 600 in the head 21. As illustrated in FIG. 3, thehead 21 includes the discharging unit 600 and a reservoir 641.

The reservoir 641 is provided for each color of ink, and an ink isintroduced from a supply port 661 to the reservoir 641. An ink issupplied from each of the ink cartridges 22 provided in the ink storingunit 8 to the supply port 661 via an ink tube.

Each of the discharging units 600 includes the piezoelectric element 60,a vibrating plate 621, a cavity (pressure chamber) 631, and the nozzle651. The vibrating plate 621 is displaced (bending vibration) by thepiezoelectric element 60 provided at the top in FIG. 3, and functions asa diaphragm that increases/decreases the internal volume of the cavity631 filled with an ink. The nozzle 651 is provided in the nozzle plate632 and is an opening portion that communicates with the cavity 631. Thecavity 631 is filled with a liquid (for example, an ink), and theinternal volume of the cavity changes due to the displacement of thepiezoelectric element 60. The nozzle 651 communicates with the cavity631 and discharges the liquid in the cavity 631 as liquid dropletsaccording to the change in the internal volume of the cavity 631.

The piezoelectric element 60 illustrated in FIG. 3 has a structure inwhich a piezoelectric body 601 is sandwiched between a pair ofelectrodes 611 and 612. A middle portion of the piezoelectric body 601having this structure bends in an up-and-down direction with theelectrodes 611 and 612 and the vibrating plate 621 with respect to bothend portions in FIG. 3 according to a voltage applied by the electrodes611 and 612. Specifically, when the voltage of the drive signal Voutbecomes higher, the piezoelectric element 60 bends upwards, and when thevoltage of the drive signal Vout becomes lower, the piezoelectricelement bends downwards. In this configuration, since the internalvolume of the cavity 631 increases when the piezoelectric element bendsupwards, an ink is drawn into the reservoir 641. On the other hand,since the internal volume of the cavity 631 decreases when thepiezoelectric element bends downwards, an ink is discharged from thenozzle 651 depending on the degree of decrease.

Without being limited to the illustrated structure, each of thepiezoelectric elements 60 may be in any form in which the piezoelectricelement 60 is deformed and a liquid such as an ink can be discharged. Inaddition, without being limited to bending vibration, each of thepiezoelectric elements 60 may have a configuration where a so-calledlongitudinal vibration is used.

In addition, each of the piezoelectric elements 60 is provided so as tocorrespond to the cavity 631 and the nozzle 651 in the head 21, and isprovided so as to correspond to the selecting unit 230 as well. For thisreason, a set of the piezoelectric element 60, the cavity 631, thenozzle 651, and the selecting unit 230 is provided for each nozzle 651.

1.3.2 Configuration of Drive Signal

FIG. 4 is a view illustrating an example of the array of the nozzles651. As illustrated in FIG. 4, the nozzles 651 are arrayed, for example,in two rows, as follows. Specifically, as for nozzles in one row, theplurality of nozzles 651 are disposed at a pitch Pv in the sub-scanningdirection Y. Two rows of nozzles are spaced away from one another at apitch Ph in the main scanning direction X. The first row nozzle and thesecond row nozzle are in a relationship of being shifted away from eachother at half the pitch Pv in the sub-scanning direction Y.

Although the nozzles 651 are provided in a pattern corresponding to eachcolor of the ink cartridges 22 to be used (for example, cyan (C),magenta (M), yellow (Y), and black (B)), for example, in the mainscanning direction X, a case where gradations are expressed with asingle color will be described to simplify the following description.

FIG. 5 is a view for illustrating basic resolution of image formation bythe nozzle array illustrated in FIG. 4. To simplify description, FIG. 5is an example of a method (first method), in which the nozzles 651discharge ink droplets one time to form one dot, and black circlesindicate dots formed by landing of ink droplets.

When the head unit 20 moves in the main scanning direction X at a speedv, a dot interval D (in the main scanning direction X) between dotsformed by landing of ink droplets as illustrated in FIG. 5 and the speedv are in a relationship as follows.

That is, in a case where one dot is formed by one time of discharging ofink droplets, the dot interval D is a value (=v/f) obtained by dividingthe speed v by an ink discharge frequency f, in other words, is adistance by which the head unit 20 moves in a period (1/f) when inkdroplets are repeatedly discharged.

In examples illustrated in FIGS. 4 and 5, a relationship of the pitch Phbeing proportional to the dot interval D by a coefficient n isestablished, such that ink droplets discharged by the two rows ofnozzles 651 land in the same rows on the printing medium P. For thisreason, as illustrated in FIG. 5, a dot interval in the sub-scanningdirection Y is half a dot interval in the main scanning direction X. Thearray of dots is not limited to the illustrated example.

High-speed printing is realized simply by increasing the speed v atwhich the head unit 20 moves in the main scanning direction X. However,simply increasing the speed v makes the dot interval D longer. For thisreason, it is necessary to increase the number of dots formed per unittime by increasing the ink discharge frequency f in order to realizehigh-speed printing with a certain degree of resolution being ensured.

Apart from a printing speed, the number of dots formed per unit area maybe increased in order to increase resolution. However, in a case ofincreasing the number of dots, dots adjacent to each other combinetogether if the used amount of ink is not small, and a printing speeddeclines if the ink discharge frequency f is not increased.

As described above, it is necessary to increase the ink dischargefrequency f in order to realize high-speed printing and high-resolutionprinting.

In addition to a method of forming one dot by discharging ink dropletsone time, there are a method of forming one dot (second method) bydischarging ink droplets two or more times per unit time, landing one ormore ink droplets discharged per unit time, and combining one or morelanded ink droplets and a method of forming two or more dots (thirdmethod) without combining the two or more ink droplets, as a method offorming a dot onto the printing medium P. In the first embodiment,according to the second method, four gradations of a “large dot”, a“medium dot”, a “small dot”, and a “non-recording (no dot)” areexpressed for one dot by discharging an ink two times at maximum.

To express the four gradations, the drive signals COM-A and COM-B areprepared and each of the drive signals has the former half pattern andthe latter half pattern in one period of dot formation in the firstembodiment. A configuration where one of the drive signals COM-A andCOM-B in the former half and the latter half of one period is selected(or not selected) according to a gradation to be expressed and thesignal is supplied to the piezoelectric element 60.

FIG. 6 is a diagram showing the waveforms of the drive signals COM-A andCOM-B. As shown in FIG. 6, the drive signal COM-A has a waveform, inwhich a trapezoidal waveform Adp1 disposed in a period T1 from the riseof the latch signal LAT to the rise of the change signal CH is followedby a trapezoidal waveform Adp2 disposed in a period T2 from the rise ofthe change signal CH to the next rise of the latch signal LAT. A periodformed of the period T1 and period T2 is set as a period Ta, and a newdot is formed onto the printing medium P for each period Ta.

In the first embodiment, the trapezoidal waveforms Adp1 and Adp2 arewaveforms that are almost the same. Each of the trapezoidal waveformssupplied to one end of the piezoelectric element 60 is a waveform, inwhich a predetermined amount of ink, specifically, a medium amount ofink is discharged from a nozzle 651 corresponding to the piezoelectricelement 60.

The drive signal COM-B has a waveform, in which a trapezoidal waveformBdp1 disposed in the period T1 is followed by a waveform of atrapezoidal waveform Bdp2, which is disposed in the period T2. Thetrapezoidal waveform Bdp1 is a waveform for slightly vibrating an ink inthe vicinity of the opening portion of the nozzle 651 and preventing anincrease in the viscosity of the ink. For this reason, even when thetrapezoidal waveform Bdp1 is supplied to one end of the piezoelectricelement 60, ink droplets are not discharged from the nozzle 651corresponding to the piezoelectric element 60. The trapezoidal waveformBdp2 is a waveform that is different from the trapezoidal waveform Adp1(Adp2). The trapezoidal waveform Bdp2 is a waveform in which a smalleramount of ink than the predetermined amount described above isdischarged from the nozzle 651 corresponding to the piezoelectricelement 60 when a drive signal having this waveform is supplied to oneend of the piezoelectric element 60.

Both of a voltage at a start timing of the trapezoidal waveforms Adp1,Adp2, Bdp1, and Bdp2 and a voltage at an end timing are the same, thatis, the voltage Vc. That is, each of the trapezoidal waveforms Adp1,Adp2, Bdp1, and Bdp2 is a waveform that starts with the voltage Vc andends with the voltage Vc.

FIG. 7 is a diagram showing a waveform of the drive signal Voutcorresponding to each of the “large dot”, the “medium dot”, the “smalldot”, and the “non-recording”, in the first embodiment.

As shown in FIG. 7, the drive signal Vout corresponding to the “largedot” has a waveform, in which the trapezoidal waveform Adp1 of the drivesignal COM-A in the period T1 is followed by the trapezoidal waveformAdp2 of the drive signal COM-A in the period T2. When the drive signalVout is supplied to one end of the piezoelectric element 60, a mediumamount of ink is discharged two times from the nozzle 651 correspondingto the piezoelectric element 60 in the period Ta. For this reason, eachink lands and coalesces to form a large dot on the printing medium P inthe period Ta.

The drive signal Vout corresponding to the “medium dot” has a waveform,in which the trapezoidal waveform Adp1 of the drive signal COM-A in theperiod T1 is followed by the trapezoidal waveform Bdp2 of the drivesignal COM-B in the period T2. When the drive signal Vout is supplied toone end of the piezoelectric element 60, a medium amount of ink and asmall amount of ink are discharged in total two times from the nozzle651 corresponding to the piezoelectric element 60 in the period Ta. Forthis reason, a medium dot is formed on the printing medium P in theperiod Ta.

The drive signal Vout corresponding to the “small dot” has a waveform,in which the voltage Vc that is a voltage immediately before being heldconstant due to a capacitive property of the piezoelectric element 60 inthe period T1 is followed by the trapezoidal waveform Bdp2 of the drivesignal COM-B in the period T2. When the drive signal Vout is supplied toone end of the piezoelectric element 60, a small amount of ink isdischarged one time from the nozzle 651 corresponding to thepiezoelectric element 60 in the period Ta. For this reason, a small dotis formed on the printing medium P in the period Ta.

The drive signal Vout corresponding to the “non-recording” has awaveform, in which the trapezoidal waveform Bdp1 of the drive signalCOM-B in the period T1 is followed by the voltage Vc that is a voltageimmediately before being held constant due to a capacitive property ofthe piezoelectric element 60 in the period T2.

When the drive signal Vout is supplied to one end of the piezoelectricelement 60, the nozzle 651 corresponding to the piezoelectric element 60vibrates slightly in the period T1 and an ink is not discharged in theperiod Ta. For this reason, an ink does not land and a dot is not formedon the printing medium P.

1.3.3 Electrical Configuration of Drive Circuit

Operation of the drive circuits 50-a and 50-b that generate the drivesignals COM-A and COM-B will be described. To describe one drive circuit50-a, out of the two drive circuits, the drive signal COM-A is generatedas follows. That is, the drive circuit 50-a, firstly, converts the drivedata dA supplied from the control signal generating unit 100 to analog,secondly, feeds the output drive signal COM-A back and corrects adeviation of a signal (attenuation signal), which is based on the drivesignal COM-A, from a target signal, with a high-frequency component ofthe drive signal COM-A to generate a modulation signal in accordancewith the corrected signal, thirdly, generates an amplified modulationsignal by switching a transistor in accordance with the modulationsignal, and fourthly, smoothes out (demodulates) the amplifiedmodulation signal with a low pass filter to output the smoothed outsignal as the drive signal COM-A.

The other drive circuit 50-b has the same configuration, and isdifferent only in terms of the fact that the drive signal COM-B isoutput from the drive data dB. In the following FIG. 8, the drivecircuits 50-a and 50-b will be described as the drive circuit 50 withoutdifferentiating between the two drive circuits.

Drive data to be input and a drive signal to be output are expressedwith dA (dB) and COM-A (COM-B), respectively. In the case of the drivecircuit 50-a, it is expressed that the drive data dA is input and thedrive signal COM-A is output. In the case of the drive circuit 50-b, itis expressed that the drive data dB is input and the drive signal COM-Bis output.

FIG. 8 is a diagram showing a circuit configuration of the drive circuit50.

Although a configuration for outputting the drive signal COM-A is shownin FIG. 8, an integrated circuit device 500 is, in fact, a circuit inwhich circuits for generating both of the two drive signals COM-A andCOM-B are packaged into one circuit.

As shown in FIG. 8, the drive circuit 50 includes the integrated circuitdevice 500, an output circuit 550, and various types of elements such asa plurality of resistances and capacitors.

The drive circuit 50 in the first embodiment includes a modulating unit510 that generates a modulation signal obtained by pulse-modulating anoriginal signal, a gate driver 520 that generates an amplified controlsignal based on the modulation signal, a transistor (a first transistorM1 and a second transistor M2) that generates an amplified modulationsignal obtained by amplifying the modulation signal based on theamplified control signal, a low pass filter 560 that demodulates theamplified modulation signal to generate a drive signal, a feedbackcircuit (a first feedback circuit 570 and a second feedback circuit 572)that feeds the drive signal back to the modulating unit 510, and astep-up circuit 540. In addition, the drive circuit 50 may include afirst power supply unit 530 that applies a signal to a terminal, whichis different from a terminal to which a drive signal of thepiezoelectric element 60 is applied.

The integrated circuit device 500 in the first embodiment includes themodulating unit 510 and the gate driver 520.

The integrated circuit device 500 outputs a gate signal (amplifiedcontrol signal) to each of the first transistor M1 and the secondtransistor M2 based on the 10-bit drive data dA (original signal) inputfrom the drive data receiving unit 330 via terminals D0 to D9. For thisreason, the integrated circuit device 500 includes a digital to analogconverter (DAC) 511, an adder 512, an adder 513, a comparator 514, anintegral attenuator 516, an attenuator 517, an inverter 515, a firstgate driver 521, a second gate driver 522, the first power supply unit530, the step-up circuit 540, and a reference voltage generating unit580.

The reference voltage generating unit 580 generates a first referencevoltage DAC_HV (reference voltage on a high-voltage side) and a secondreference voltage DAC_LV (reference voltage on a low-voltage side),which are regulated by a regulating signal, and supplies the voltages tothe DAC 511.

The DAC 511 converts the drive data dA, in which the waveform of thedrive signal COM-A is defined, to an underlying drive signal Aa, whichis a voltage between the first reference voltage DAC_HV and the secondreference voltage DAC_LV, and supplies the signal to an input end (+) ofthe adder 512. The maximum value and the minimum value of the voltageamplitude of the underlying drive signal Aa are determined by the firstreference voltage DAC_HV and the second reference voltage DAC_LV (forexample, approximately 1 to 2 V) respectively. When the voltage isamplified, the drive signal COM-A is obtained. That is, the underlyingdrive signal Aa is a target signal before the amplification of the drivesignal COM-A.

The integral attenuator 516 attenuates and integrates a voltage from aterminal Out, which is input via a terminal Vfb, that is, the drivesignal COM-A to supply to an input end (−) of the adder 512.

The adder 512 supplies a signal Ab, which is an integrated voltageobtained by deducting a voltage from the input end (−) from a voltagefrom the input end (+), to an input end (+) of the adder 513.

A power supply voltage of a circuit ranging from the DAC 511 to theinverter 515 is 3.3 V (a voltage VDD supplied from a power supplyterminal Vdd) with a low amplitude. For this reason, since there is acase where the voltage of the drive signal COM-A exceeds 40 V at maximumwhile the voltage of the underlying drive signal Aa is onlyapproximately 2 V at maximum, the voltage of the drive signal COM-A isattenuated by the integral attenuator 516 in order to match amplituderanges of both voltages when acquiring a deviation.

The attenuator 517 attenuates a high-frequency component of the drivesignal COM-A input via a terminal Ifb to supply to an input end (−) ofthe adder 513. The adder 513 supplies a signal As, which is a voltageobtained by subtracting a voltage from the input end (−) from a voltagefrom the input end (+), to the comparator 514. As in the integralattenuator 516, attenuation by the attenuator 517 is for matching theamplitudes in feeding back the drive signal COM-A.

The voltage of the signal As output from the adder 513 is a voltageobtained by deducting the attenuation voltage of a signal supplied tothe terminal Vfb from the voltage of the underlying drive signal Aa andsubtracting the attenuation voltage of a signal supplied to the terminalIfb. For this reason, the voltage of the signal As output from the adder513 can be referred to as a signal obtained by correcting a deviation ofthe attenuation voltage of the drive signal COM-A, which is output fromthe terminal Out, from the voltage of the underlying drive signal Aa,which is a target, with the high-frequency component of the drive signalCOM-A.

Based on a subtraction voltage from the adder 513, the comparator 514outputs a modulation signal Ms obtained by pulse-modulation as follows.Specifically, the comparator 514 outputs the modulation signal Ms, whichis at a level H when the signal As output from the adder 513 is equal toor larger than a voltage threshold Vth1, in the case of a voltage rise,and outputs the modulation signal Ms, which is at a level L when thesignal As falls short of a voltage threshold Vth2, in the case of avoltage drop. As will be described later, a voltage threshold is set soas to satisfy a relationship of Vth1>Vth2.

The modulation signal Ms from the comparator 514 is supplied to thesecond gate driver 522 through logic inversion by the inverter 515. Themodulation signal Ms is supplied to the first gate driver 521 withoutgoing through logic inversion. For this reason, logic levels supplied tothe first gate driver 521 and the second gate driver 522 are in arelationship exclusive to each other.

The logic levels supplied to the first gate driver 521 and the secondgate driver 522 may be controlled in terms of timing such that, inreality, the logic levels do not come at a level H simultaneously (suchthat the first transistor M1 and the second transistor M2 are not turnedon simultaneously). For this reason, in the strict sense, the term“exclusive” means that the logic levels do not simultaneously come at alevel H (the first transistor M1 and the second transistor M2 are notturned on simultaneously).

Although the term “modulation signal” means the modulation signal Ms inthe narrow sense, the negative signal of the modulation signal Ms isalso included in the modulation signal, considering thatpulse-modulation is performed according to the underlying drive signalAa. That is, a modulation signal obtained by pulse-modulation accordingto the underlying drive signal Aa includes not only the modulationsignal Ms but also a signal obtained by inverting the logic level of themodulation signal Ms and a signal controlled in terms of timing.

Since the comparator 514 outputs the modulation signal Ms, a circuitranging over to the comparator 514 or the inverter 515, that is,including the adder 512, the adder 513, the comparator 514, the inverter515, the integral attenuator 516, and the attenuator 517, corresponds tothe modulating unit 510 that generates a modulation signal.

The first gate driver 521 level-shifts a low logic amplitude, which isan output signal of the comparator 514, so as to be a high logicamplitude to output from a terminal Hdr. Out of power supply voltages ofthe first gate driver 521, a higher voltage is a voltage applied via aterminal Bst, and a lower voltage is a voltage applied via a terminalSw. The terminal Bst is connected to one end of a capacitor C5 and acathode electrode of a diode D10 for backflow prevention. The terminalSw is connected to a source electrode of the first transistor M1, adrain electrode of the second transistor M2, the other end of thecapacitor C5, and one end of an inductor L1. An anode electrode of thediode D10 is connected to a terminal Gvd, and a voltage Vm (for example,7.5 V) output by the step-up circuit 540 is applied thereto. Therefore,a potential difference between the terminal Bst and the terminal Sw issubstantially equal to a potential difference between both ends of thecapacitor C5, that is, the voltage Vm (for example, 7.5 V).

The second gate driver 522 operates on a low electric potential side ofthe first gate driver 521. The second gate driver 522 level-shifts a lowlogic amplitude (level L: 0 V and level H: 3.3 V), which is an outputsignal of the inverter 515, to a high logic amplitude (for example,level L: 0 V and level H: 7.5 V) to output from a terminal Ldr. Out ofpower supply voltages of the second gate driver 522, the voltage Vm (forexample, 7.5 V) is applied as a higher voltage, and a zero voltage isapplied via a ground terminal Gnd as a lower voltage. That is, theground terminal Gnd is earthed to the ground. In addition, the terminalGvd is connected to the anode electrode of the diode D10.

The first transistor M1 and the second transistor M2 are, for example,N-channel field effect transistors (FET). In the first transistor M1 ona high side, out of the two transistors, a voltage Vh (for example, 42V) is applied to a drain electrode and a gate electrode is connected tothe terminal Hdr via a resistance R1. In the second transistor M2 on alow side, a gate electrode is connected to the terminal Ldr via aresistance R2 and a source electrode is earthed to the ground.

Therefore, when the first transistor M1 is turned off and the secondtransistor M2 is turned on, the voltage of the terminal Sw is 0 V andthe voltage Vm (for example, 7.5 V) is applied to the terminal Bst. Onthe other hand, when the first transistor M1 is turned on and the secondtransistor M2 is turned off, Vh (for example, 42 V) is applied to theterminal Sw and Vh+Vm (for example, 49.5 V) is applied to the terminalBst.

That is, with the capacitor C5 being as a floating power supply, thefirst gate driver 521 outputs an amplified control signal, of whichlevel L is 0 V and level H is Vm (for example, 7.5 V), or of which levelL is approximately Vh (for example, 42 V) and level H is approximatelyVh+Vm (for example, 49.5 V), since a reference electric potential (theelectric potential of the terminal Sw) changes to 0 V or Vh (forexample, 42 V) according to operation of the first transistor M1 and thesecond transistor M2. The second gate driver 522 outputs an amplifiedcontrol signal, of which level L is 0 V and level H is Vm (for example,7.5 V), since a reference electric potential (the electric potential ofthe terminal Gnd) is fixed at 0 V regardless of operation of the firsttransistor M1 and the second transistor M2.

The other end of the inductor L1 is the terminal Out, which is an outputof the drive circuit 50, and the drive signal COM-A from the terminalOut is supplied to the head unit 20 via the cable 19 (refer to FIG. 2).

The terminal Out is connected to each of one end of a capacitor C1, oneend of a capacitor C2, and one end of a resistance R3. Out of the aboveelements, the other end of the capacitor C1 is earthed to the ground.For this reason, the inductor L1 and the capacitor C1 function as thelow pass filter 560 that smoothes out an amplified modulation signal,which appears at a connection point between the first transistor M1 andthe second transistor M2.

The other end of the resistance R3 is connected to the terminal Vfb andone end of a resistance R4, and the voltage Vh is applied to the otherend of the resistance R4. Accordingly, the drive signal COM-A, which haspassed through the first feedback circuit 570 (circuit configured of theresistance R3 and the resistance R4) from the terminal Out, is pulled upto be fed back to the terminal Vfb.

The other end of the capacitor C2 is connected to one end of aresistance R5 and one end of a resistance R6. Out of the above elements,the other end of the resistance R5 is earthed to the ground. For thisreason, the capacitor C2 and the resistance R5 function as a high passfilter that allows a high-frequency component of the drive signal COM-Afrom the terminal Out having a frequency that is equal to or higher thana cut-off frequency to pass therethrough. The cut-off frequency of thehigh pass filter is set to, for example, approximately 9 MHz.

The other end of the resistance R6 is connected to one end of acapacitor C4 and one end of a capacitor C3. Out of the above elements,the other end of the capacitor C3 is earthed to the ground. For thisreason, the resistance R6 and the capacitor C3 function as a low passfilter that allows a low-frequency component having a frequency that isequal to or lower than a cut-off frequency to pass therethrough, out ofsignal components which have passed through the high pass filter. Thecut-off frequency of the low pass filter is set to, for example,approximately 160 MHz.

Since the cut-off frequency of the high pass filter is set so as to belower than the cut-off frequency of the low pass filter, the high passfilter and the low pass filter function as a band pass filter thatallows a high-frequency component of the drive signal COM-A in apredetermined frequency range to pass therethrough.

The other end of the capacitor C4 is connected to the terminal Ifb ofthe integrated circuit device 500. Accordingly, out of high-frequencycomponents of the drive signal COM-A, which has passed through thesecond feedback circuit 572 (circuit configured of the capacitor C2, theresistance R5, the resistance R6, the capacitor C3, and the capacitorC4) functioning as the band pass filter, a direct current component iscut and fed back to the terminal Ifb.

The drive signal COM-A output from the terminal Out is a signal obtainedby smoothing out an amplified modulation signal at the connection point(terminal Sw) between the first transistor M1 and the second transistorM2 with the low pass filter 560 configured of the inductor L1 and thecapacitor C1. Since the drive signal COM-A is fed back to the adder 512via the terminal Vfb after being integrated and subtracted,self-oscillation occurs at a frequency determined by a delay of feedback(a sum of a delay caused by smoothing-out of the inductor L1 and thecapacitor C1 and a delay caused by the integral attenuator 516) and atransfer function of the feedback.

However, since the amount of a delay through a feedback path via theterminal Vfb is large, there is a case where the feedback via theterminal Vfb only is not enough to make the frequency ofself-oscillation higher to an extent that the accuracy of the drivesignal COM-A can be sufficiently ensured.

Thus, by providing a path through which a high-frequency component ofthe drive signal COM-A is fed back via the terminal Ifb in addition tothe path via the terminal Vfb, a delay can be made shorter from aperspective of the entire circuit in the first embodiment. For thisreason, the frequency of the signal As, which is obtained by adding ahigh-frequency component of the drive signal COM-A to the signal Ab,becomes higher to an extent that the accuracy of the drive signal COM-Acan be sufficiently ensured, compared to a case where there is no pathvia the terminal Ifb.

FIG. 9 is a diagram showing the waveform of the underlying drive signalAa in association with the waveforms of the signal As and the modulationsignal Ms.

As shown in FIG. 9, the signal As has a triangular wave, and theoscillation frequency thereof fluctuates according to the voltage (inputvoltage) of the underlying drive signal Aa. Specifically, theoscillation frequency becomes the highest in a case where an inputvoltage is an intermediate value. The oscillation frequency becomeslower as an input voltage becomes higher than the intermediate value oras an input voltage becomes lower than the intermediate value.

In addition, the upward inclination (rise of the voltage) and thedownward inclination (drop of the voltage) of the triangular wave of thesignal As are almost the same when an input voltage is close to anintermediate value. For this reason, the duty ratio of the modulationsignal Ms, which is a result obtained by the comparator 514 comparingthe signal As to the voltage thresholds Vth1 and Vth2, is almost 50%.When an input voltage becomes higher than the intermediate value, thedownward inclination of the signal As becomes moderate. For this reason,a period for which the modulation signal Ms is at a level H becomesrelatively longer and a duty ratio becomes higher. As an input voltagebecomes lower than the intermediate value, the upward inclination of thesignal As becomes moderate. For this reason, a period for which themodulation signal Ms is at a level H becomes relatively shorter and aduty ratio becomes lower.

For this reason, the modulation signal Ms becomes a pulse densitymodulation signal as follows. That is, the duty ratio of the modulationsignal Ms is almost 50% when the input voltage has the intermediatevalue. As the input voltage becomes higher than the intermediate value,the duty ratio becomes higher. As the input voltage becomes lower thanthe intermediate value, the duty ratio becomes lower.

The first gate driver 521 turns the first transistor M1 on/off based onthe modulation signal Ms. That is, the first gate driver 521 turns thefirst transistor M1 on when the modulation signal Ms is at a level H,and turns the first transistor off when the modulation signal Ms is at alevel L. The second gate driver 522 turns the second transistor M2on/off based on a logic inversion signal of the modulation signal Ms.That is, the second gate driver 522 turns the second transistor M2 offwhen the modulation signal Ms is at a level H, and turns the secondtransistor on when the modulation signal Ms is at a level L.

Therefore, the voltage of the drive signal COM-A, which is obtained bysmoothing out the amplified modulation signal at the connection pointbetween the first transistor M1 and the second transistor M2 with theinductor L1 and the capacitor C1, becomes higher as the duty ratio ofthe modulation signal Ms becomes higher, and becomes lower as the dutyratio becomes lower. Consequently, the drive signal COM-A is controlledso as to be a signal obtained by increasing and power-amplifying thevoltage of the underlying drive signal Aa and is output.

Since pulse density modulation is used, the drive circuit 50 isadvantageous in that the width of change in the duty ratio can be madelarger compared to pulse width modulation in which a modulationfrequency is fixed.

That is, since a minimum positive pulse width and a minimum negativepulse width, which can be dealt by the entire circuit, are restricted byproperties of the circuit, only a predetermined range (for example, arange of 10% to 90%) can be ensured as the width of change in the dutyratio in pulse width modulation when a frequency is fixed. On the otherhand, since the oscillation frequency becomes lower as an input voltagemoves away from the intermediate value in pulse density modulation, theduty ratio can be made higher in a region with a high input voltage andthe duty ratio can be made lower in a region with a low input voltage.For this reason, in self-oscillation pulse density modulation, a widerrange (for example, a range of 5% to 95%) can be ensured as the width ofchange in the duty ratio.

The drive circuit 50 self-oscillates and a circuit that generatescarrier waves having a high frequency, such as forced-oscillation, isnot necessary. For this reason, the drive circuit is advantageous inthat it is easy to integrate circuits other than a circuit dealing witha high voltage, that is, a portion of the integrated circuit device 500.

Since there is not only the path via the terminal Vfb but also the paththrough which a high-frequency component is fed back via the terminalIfb as a feedback path of the drive signal COM-A in the drive circuit50, a delay from a perspective of the entire circuit becomes shorter.For this reason, since the frequency of self-oscillation becomes higher,the drive circuit 50 can accurately generate the drive signal COM-A.

Referring back to FIG. 8, in an example shown in FIG. 8, the resistanceR1, the resistance R2, the first transistor M1, the second transistorM2, the capacitor C5, the diode D10, and the low pass filter 560configure the output circuit 550 that generates an amplified controlsignal based on a modulation signal and generates a drive signal basedon the amplified control signal to output to a capacitive load(piezoelectric element 60).

The first power supply unit 530 applies a signal to a terminal that isdifferent from a terminal to which a drive signal for the piezoelectricelement 60 is applied. The first power supply unit 530 is configured of,for example, a constant voltage circuit such as a bandgap referencecircuit. The first power supply unit 530 outputs the voltage VBS from aterminal Vbs. In the example shown in FIG. 8, the first power supplyunit 530 generates the voltage VBS with a ground electric potential ofthe ground terminal Gnd being as reference.

The step-up circuit 540 supplies power to the gate driver 520. In theexample shown in FIG. 8, the step-up circuit 540 steps up the voltageVDD supplied from the power supply terminal Vdd with the ground electricpotential of the ground terminal Gnd being as reference and generatesthe voltage Vm, which is a power supply voltage on a high electricpotential side of the second gate driver 522. Although the step-upcircuit 540 can be configured of a charge pump circuit and a switchingregulator, a case where the step-up circuit is configured of a chargepump circuit can better suppress the generation of a noise compared to acase where the step-up circuit is configured of a switching regulator.For this reason, since the drive circuit 50 can more accurately generatethe drive signal COM-A and can control a voltage applied to thepiezoelectric element 60 with high accuracy, the accuracy of discharginga liquid can be improved. Since a power generating unit of the gatedriver 520 is miniaturized by configuring the step-up circuit of thecharge pump circuit, it is possible to mount the gate driver on theintegrated circuit device 500, and the entire area of the drive circuit50 can be significantly reduced compared to a case where the powergenerating unit of the gate driver 520 is configured outside theintegrated circuit device 500.

1.3.4 Configuration of Selection Control Unit and Selecting Unit

FIG. 10 is a diagram showing a configuration of the selection controlunit 210. As shown in FIG. 10, the clock signal Sck, the print datasignal SI, the latch signal LAT, and the change signal CH are suppliedto the selection control unit 210. A set of a shift register (S/R) 212,a latch circuit 214, and a decoder 216 is provided in the selectioncontrol unit 210 so as to correspond to the each of the piezoelectricelements 60 (nozzles 651).

The print data signal SI is in total 2 m bit signals including 2-bitprint data (SIH, SIL) for selecting any one of the “large dot”, the“medium dot”, the “small dot”, and the “non-recording” with respect toeach of the m discharging units 600.

The print data signal SI is serially supplied from the control signalrestoring unit 320 in synchronization with the clock signal Sck. Theshift register 212 has a configuration of temporarily holding theserially supplied print data signal SI for each of two bits of printdata (SIH, SIL) corresponding to each of the nozzles 651.

Specifically, a configuration, in which the same number of the shiftregisters 212 as the number of stages that correspond to thepiezoelectric elements 60 (nozzles) are cascade-connected to each otherand the serially supplied print data signal SI is subsequentlytransmitted to the next stage in accordance with the clock signal Sck,is adopted.

When the number of the piezoelectric elements 60 is m (m is a pluralnumber), stages are expressed as a first stage, a second stage, . . . ,and a mth stage in order of being on an upstream side where the printdata signal SI is supplied in order to differentiate between the shiftregisters 212.

Each of the m latch circuits 214 latches 2-bit print data (SIH, SIL)held by each of the m shift registers 212 upon the rise of the latchsignal LAT.

Each of the m decoders 216 decodes the 2-bit print data (SIH, SIL)latched by each of the m latch circuits 214, outputs selection signalsSa and Sb for each of the periods T1 and T2 defined by the latch signalLAT and the change signal CH, and defines the selection by the selectingunit 230.

FIG. 11 is a diagram showing the contents of decoding by the decoder216. For example, when the latched 2-bit print data (SIH, SIL) is (1,0), the decoder 216 sets the logic levels of the selection signals Saand Sb to levels H and L respectively in the period T1, and to levels Land H respectively in the period T2 and outputs the signals.

The logic levels of the selection signals Sa and Sb are shifted by alevel shifter (not illustrated) to higher amplitude logic than the logiclevels of the clock signal Sck, the print data signal SI, the latchsignal LAT, and the change signal CH.

FIG. 12 is a diagram showing a configuration of the selecting unit 230corresponding to one piezoelectric element 60 (nozzle 651).

As shown in FIG. 12, the selecting unit 230 has inverters (NOT gate) 232a and 232 b and transfer gates 234 a and 234 b.

The selection signal Sa from the decoder 216 is supplied to a positivecontrol end of the transfer gate 234 a, to which a circle is notattached, while being logically inverted by the inverter 232 a and beingsupplied to a negative control end of the transfer gate 234 a, to whicha circle is attached. Similarly, the selection signal Sb is supplied toa positive control end of the transfer gate 234 b while being logicallyinverted by the inverter 232 b and being supplied to a negative controlend of the transfer gate 234 b.

The drive signal COM-A is supplied to an input end of the transfer gate234 a and the drive signal COM-B is supplied to an input end of thetransfer gate 234 b. Output ends of the transfer gates 234 a and 234 bare commonly connected to each other, and the drive signal Vout isoutput to the head 21 via a common connection terminal.

When the selection signal Sa is at a level H, the transfer gate 234 aelectrically connects between the input end and the output end(switching on). When the selection signal Sa is at a level L, thetransfer gate electrically disconnects between the input end and theoutput end (switching off). Similarly, the transfer gate 234 b alsoswitches on/off between the input end and the output end according tothe selection signal Sb.

Next, operation of the selection control unit 210 and operation of theselecting unit 230 will be described with reference to FIG. 13.

The print data signal SI is serially supplied in synchronization withthe clock signal Sck from the control signal restoring unit 320 and issubsequently transmitted to the shift register 212 corresponding to eachnozzle. When the control signal restoring unit 320 stops supplying theclock signal Sck, the 2-bit print data (SIH, SIL) corresponding to eachof the nozzles comes to a state of being held in each of the shiftregisters 212. The print data signal SI is supplied to the shiftregisters 212 corresponding to the nozzles at the last mth stage, . . ., the second stage, and the first stage in this order.

When the latch signal LAT rises, each of the latch circuits 214simultaneously latches the 2-bit print data (SIH, SIL) held by each ofthe shift registers 212. In FIG. 13, LT1, LT2, . . . , and LTm indicate2-bit print data (SIH, SIL) latched by the latch circuits 214corresponding to the shift registers 212 at the first stage, the secondstage, . . . , and the mth stage.

The decoder 216 outputs contents as shown in FIG. 11 such as the logiclevels of the selection signals Sa and Sb in each of the periods T1 andT2 according to the size of a dot defined by the latched 2-bit printdata (SIH, SIL).

That is, the decoder 216 sets the selection signals Sa and Sb to levelsH and L in the period T1 and also to levels H and L in the period T2 ina case where the print data (SIH, SIL) is (1, 1) and the size of a dotis defined as a large dot. The decoder 216 sets the selection signals Saand Sb to levels H and L in the period T1 and to levels L and H in theperiod T2 in a case where the print data (SIH, SIL) is (1, 0) and thesize of a dot is defined as a medium dot. The decoder 216 sets theselection signals Sa and Sb to levels L and L in the period T1 and tolevels L and H in the period T2 in a case where the print data (SIH,SIL) is (0, 1) and the size of a dot is defined as a small dot. Thedecoder 216 sets the selection signals Sa and Sb to levels L and H inthe period T1 and to levels L and L in the period T2 in a case where theprint data (SIH, SIL) is (0, 0) and non-recording is defined.

When the print data (SIH, SIL) is (1, 1), the selecting unit 230 selectsthe drive signal COM-A (trapezoidal waveform Adp1) since the selectionsignals Sa and Sb are at levels H and L in the period T1 and selects thedrive signal COM-A (trapezoidal waveform Adp2) since the selectionsignals Sa and Sb are at levels H and L also in the period T2. As aresult, the drive signal Vout corresponding to the “large dot” shown inFIG. 7 is generated.

When the print data (SIH, SIL) is (1, 0), the selecting unit 230 selectsthe drive signal COM-A (trapezoidal waveform Adp1) since the selectionsignals Sa and Sb are at levels H and L in the period T1 and selects thedrive signal COM-B (trapezoidal waveform Bdp2) since the selectionsignals Sa and Sb are at levels L and H in the period T2. As a result,the drive signal Vout corresponding to the “medium dot” shown in FIG. 7is generated.

When the print data (SIH, SIL) is (0, 1), the selecting unit 230 doesnot select either of the drive signals COM-A and COM-B since theselection signals Sa and Sb are at levels L and L in the period T1 andselects the drive signal COM-B (trapezoidal waveform Bdp2) since theselection signals Sa and Sb are at levels L and H in the period T2. As aresult, the drive signal Vout corresponding to the “small dot” shown inFIG. 7 is generated.

When the print data (SIH, SIL) is (0, 0), the selecting unit 230 selectsthe drive signal COM-B (trapezoidal waveform Bdp1) since the selectionsignals Sa and Sb are at levels L and H in the period T1 and does notselect either of the drive signals COM-A and COM-B since the selectionsignals Sa and Sb are at levels L and L also in the period T2. As aresult, the drive signal Vout corresponding to the “non-recording” shownin FIG. 7 is generated.

Since either of the drive signals COM-A and COM-B are not selected in aperiod when the selection signals Sa and Sb are at levels L and L, oneend of the piezoelectric element 60 is opened. However, the drive signalVout is held at the immediately before voltage Vc due to a capacitiveproperty of the piezoelectric element 60.

The drive signals COM-A and COM-B in the first embodiment are merelyexamples. In fact, various combinations of waveforms prepared in advanceaccording to a speed at which the head unit 20 moves and thecharacteristics of a printing medium are used.

Although an example in which the piezoelectric elements 60 bend upwardswith a rise in the voltage has been described herein, the piezoelectricelements 60 bend downwards with a rise in the voltage when a voltagesupplied to the electrodes 611 and 612 is reversed. For this reason, ina configuration where the piezoelectric elements 60 bend downwards witha rise in the voltage, the drive signals COM-A and COM-B given asexamples in the first embodiment have waveforms which are inverted withthe voltage Vc being as reference.

1.4 Configuration of Printing Unit

A configuration of the printing unit 5 in the first embodiment will bedescribed with reference to FIGS. 14 and 15. FIG. 14 is a viewillustrating the configuration of the printing unit 5 when seen in thesub-scanning direction Y, and FIG. 15 is a view illustrating an internalconfiguration of the carriage 24 when seen in the main scanningdirection X. In FIGS. 14 and 15, a side of the main scanning direction Xwhere the control unit 10 is provided will be referred to as X1, and aside opposite thereto will be referred to as X2. An upstream side of thetransporting direction of the printing medium P, which is thesub-scanning direction Y, will be referred to as Y1, and a downstreamside will be referred to as Y2. A vertically lower side of the verticaldirection Z will be referred to as Z1, and a vertically upper side willbe referred to as Z2.

The printing unit 5 is configured so as to include the control unit 10,the head unit 20, the drive unit 30, the cables 19, the carriage guideshaft 32, a platen 33, a capping mechanism 35, and the maintenancemechanism 80.

The carriage guide shaft 32 is provided in the main scanning direction Xand supports the head unit 20. That is, the head unit 20 moves(reciprocates) within an area of a movable region R along the carriageguide shaft 32 based on control by the carriage moving mechanism 41(refer to FIG. 2).

The head unit 20 is configured so as to include the carriage 24 and thehead 21 mounted on the carriage 24.

The carriage 24 includes a carriage main body 241 which has an L-shapewhen seen in the main scanning direction X, a carriage supporting unit242 which is connected to the carriage guide shaft 32, and a carriagecover 243 which is included so as to make a closed space between thecarriage main body 241 and the carriage supporting unit 242.

The carriage main body 241 is configured by the head 21 and a signalprocessing circuit substrate 36, on which a plurality of signalprocessing units (the control signal receiving unit 310, the controlsignal restoring unit 320, the selection control unit 210, and theselecting units 230 (refer to FIG. 2)) are mounted, being mounted.

The head 21 is mounted on the Z1 side of the carriage 24, and thenozzles 651 and the printing medium P are provided so as to oppose eachother through an opening portion (not illustrated) of the carriage 24.

The signal processing circuit substrate 36 is provided on the Z2 side ofthe head 21 and is connected to the cables 19. The signal processingcircuit substrate 36 generates the drive signal Vout in accordance witha plurality of signal processing units (the control signal receivingunit 310, the control signal restoring unit 320, the selection controlunit 210, the selecting units 230, and the state signal generating unit380 (refer to FIG. 2)), and outputs the signal to the head 21. The head21 discharges an ink supplied from the ink storing unit 8 as inkdroplets onto the printing medium P based on the input drive signalVout.

The carriage supporting unit 242 is included on an upper (Z2 side) rear(Y1 side) portion of the carriage main body 241, and a front end portionthereof is fixed to the carriage main body 241.

The carriage supporting unit 242 has an insertion-hole 37. By insertingthe carriage guide shaft 32 into the insertion-hole 37, the carriagesupporting unit 242 is supported by the carriage guide shaft 32 alongwith the carriage main body 241. In addition, the cables 19 are insertedin the carriage supporting unit 242. The cables 19 are connected to thesignal processing circuit substrate 36 mounted on the carriage main body241 by going through the inside of the carriage supporting unit 242.

That is, by the carriage guide shaft 32 supporting the carriage 24, thehead unit 20 moves (reciprocates) within the area of the movable regionR along the carriage guide shaft 32 based on control by the carriagemoving mechanism 41 (refer to FIG. 2).

The platen 33 is provided on a surface that is different from a surfaceof the printing medium P that opposes the head 21. A roller (notillustrated) that transports the printing medium P is provided on theplaten 33, transports the printing medium P in the sub-scanningdirection Y, and holds the printing medium P on the Z1 side when inkdroplets are discharged on the printing medium P.

A home position is set on the X1 side of the platen 33. The homeposition is a starting point of movement (reciprocation) of the headunit 20, and the capping mechanism 35, which seals a nozzle formedsurface of the head 21, is provided at the home position. In addition,the home position is also a position where the head unit 20 stands bywhen the liquid discharging apparatus 1 does not execute printing.

The maintenance mechanism 80 is provided on the X2 side of the platen33. The maintenance mechanism 80 performs cleaning processing (pumpingprocessing), in which thickened inks and bubbles in the dischargingunits 600 are suctioned by a tube pump (not illustrated), and wipingprocessing, in which foreign substances, such as paper dust stuck aroundthe nozzles of the discharging units 600, are wiped off by a wiper, asmaintenance processing. It is preferable that the execution of themaintenance processing be performed outside a printing region.Accordingly, unnecessary mist generated during executing maintenanceprocessing sticks to the printing region (platen 33), and thereby apossibility that the printing medium P becomes dirty can be reduced.

The drive unit 30 is connected to the head unit 20 by the cable 19 (FFC194). When seen horizontally with respect to a discharge surface in thesub-scanning direction Y, the drive unit 30 is provided outside themovable region R of the carriage 24 and is provided on an upper (Z2)side of the discharge surface, from which the head 21 discharges inkdroplets onto the printing medium P, in the vertical direction Z. Forexample, the drive unit may be provided between the operation unit 7 andthe ink storing unit 8 illustrated in FIG. 1.

By the drive unit 30 being included outside the movable region R of thecarriage 24 and on the upper (Z2) side of the discharge surface in thevertical direction Z, the sticking of ink droplets discharged from thehead unit 20 to the drive unit 30 is reduced. Accordingly, it ispossible for the drive unit 30 to reduce the occurrence of a defect suchas an insulation failure caused by sticking of ink droplets, and thusthe reliability of the drive unit 30 can be improved.

The control unit 10 is connected to the drive unit 30 by the cable 19(FFC 192 shown in FIG. 2). When seen horizontally with respect to thedischarge surface in the sub-scanning direction Y, the control unit isprovided outside the movable region R of the carriage 24 and is providedon a lower (Z1) side of the drive unit 30 in the vertical direction Z.For example, the control unit may be provided between the operation unit7 and the ink storing unit 8 illustrated in FIG. 1.

By the control unit 10 being included outside the region where thecarriage 24 moves, the sticking of ink droplets discharged from the headunit 20 to the control unit 10 is reduced. Accordingly, it is possiblefor the control unit 10 to reduce the occurrence of a defect such as aninsulation failure caused by sticking of ink droplets, and thus thereliability of the control unit 10 can be improved.

By disposing the drive unit 30 at a position higher than the controlunit 10, heat generated in the drive unit 30 convects to the Z2 side inthe vertical direction Z. For this reason, it is possible to reduce aneffect of the heat generated in the drive unit 30 on the control unit10, and thus the occurrence of a breakdown (for example, a short life)of the control unit 10 due to the heat can be suppressed.

1.5 Configuration of Drive Unit and Drive Circuit Substrate

FIGS. 16 and 17 are views for illustrating a configuration of the driveunit 30. FIG. 16 is an exploded perspective view schematicallyillustrating the configuration of the drive unit 30, and FIG. 17 is aschematic view illustrating the layout of a drive circuit substrate 420included in the drive unit 30. In FIGS. 16 and 17, a direction x, adirection y, and a direction z, which are orthogonal to each other, areillustrated and description will be given.

As illustrated in FIG. 16, the drive unit 30 is configured so as toinclude a case 410, the drive circuit substrate 420, a heat dissipatingfin 470, and a heat dissipating fan 480.

The drive circuit substrate 420 (an example of a “drive circuitsubstrate”) includes a substrate 430, and an input unit 440, an outputunit 450, and a drive signal generating unit 460 are included on thesubstrate 430. The drive circuit substrate 420 will be described withreference to FIG. 17.

FIG. 17 is a schematic view illustrating the layout of the drive circuitsubstrate 420. The substrate 430 is substantially rectangular, and isformed of a short side 431 and a short side 432, which extend in thedirection y and oppose each other, and a long side 433 and a long side434, which extend in the direction x and oppose each other.

The input unit 440 is configured so as to include a plurality of (threein the first embodiment) connectors 441, which are arranged along thelong side 433 from a short side 431 side to a short side 432 side. Thecable 19 (FFC 192) (refer to FIG. 2) is connected to each of theplurality of connectors 441, and signals including the original drivedifferential signals dDSA and dDSB and a power supply voltage foroperating the drive unit 30 are input from the control unit 10 into theeach of the plurality of connectors.

For example, the cable 19 through which signals including the originaldrive differential signals dDSA and dDSB are transmitted may beconnected to any one of the plurality of connectors 441, the cable 19through which signals including a power supply voltage is transmittedmay be connected to another of the connectors 441, and the cable 19through which a ground electric potential is transmitted may beconnected to still another of the connectors 441. The number of theconnectors 441 included in the input unit 440 and input signals are notlimited thereto.

In the first embodiment, signals input into the drive unit 30 aresignals including the original drive differential signals dDSA and dDSBhaving weak voltages and a power supply voltage which is a high voltagefor operating the drive unit 30. Therefore, it is possible to reducemutual interference between transmitted signals by configuring the cable19 and the connector 441 through which the original drive differentialsignals dDSA and dDSB having weak voltages are transmitted and the cable19 and the connector 441 through which a power supply voltage that is ahigh voltage is transmitted of the different cables 19.

The output unit 450 is configured so as to include a plurality of (eightin the first embodiment) connectors 451, which are arranged along thelong side 434 from the short side 431 side to the short side 432 side.The cable 19 (FFC 194) (refer to FIG. 2) is connected to each of theplurality of connectors 451, and signals including the drive signalsCOM-A and COM-B and the voltage VBS are output to the head unit 20.

For example, the cable 19 through which signals including the drivesignal COM-A are transmitted may be connected to any one of theplurality of connectors 451, the cable 19 through which signalsincluding the drive signal COM-B are transmitted may be connected toanother of the connectors 451, and the cable 19 through which signalsincluding the voltage VBS are transmitted may be connected to stillanother of the plurality of connectors 451.

In addition, for example, the cable 19 through which signals includingthe drive signal COM-A and the voltage VBS are transmitted may beconnected to any one of the plurality of connectors 451, and the cable19 through which signals including the drive signal COM-B and thevoltage VBS are transmitted may be connected to another of the pluralityof connectors 451.

The same signals may be transmitted through some of the plurality ofcables 19 connected to the plurality of connectors 451. The number ofthe connectors 451 included in the output unit 450 and output signalsare not limited thereto.

By the drive signals COM-A and COM-B output by the drive unit 30increasing the number of the driven heads 21, an output currentincreases. For this reason, it is preferable that the cable 19 (FFC 194)be configured of a plurality of cables. Accordingly, it is possible tosuppress an increase in the amount of a current flowing in one cable.Thus, it is possible to reduce stray resistance and stray inductanceoccurring in cables. As the cable 19 (FFC 194) is configured of aplurality of cables, a configuration where the plurality of connectors451 are included in the output unit 450 is adopted.

The drive signal generating unit 460 is configured of a plurality of(four in the first embodiment) capacitors 461 and the plurality of (fourin the first embodiment) drive circuits 50, and is provided on the shortside 432 side of the substrate 430.

At this time, a distance between the connector 441 (an example of an“input connector”) and the connector 451 (an example an “outputconnector”) may be shorter than a distance between the drive circuit 50and the connector 441, and the distance between the connector 441 andthe connector 451 may be shorter than the distance between the drivecircuit 50 and the connector 451. Specifically, on the substrate 430 ofthe drive circuit substrate 420, the input unit 440 including theconnectors 441 and the output unit 450 including the connectors 451 areprovided on the short side 431 side and the drive signal generating unit460 including the drive circuit 50 is provided on the short side 432side.

The plurality of drive circuits 50 are arranged along the short side 432from the long side 433 side to the long side 434 side. The capacitor 461on the short side 431 side is provided for each of the plurality ofdrive circuits 50. The plurality of capacitors 461 are provided so as tocorrespond to the plurality of drive circuits 50 respectively, andstabilize a power supply voltage supplied to each of the plurality ofdrive circuits 50.

Each of the drive circuits 50 is configured so as to include theintegrated circuit device 500, the first transistor M1, the secondtransistor M2, and the inductor L1.

The inductors L1 are provided on the short side 432 side of the drivecircuits 50. The first transistors M1 and the second transistors M2 arearranged in the direction y on the short side 431 side of the inductorsL1. In addition, the integrated circuit devices 500 are also provided onthe short side 431 side of the arranged first transistors M1 and thesecond transistors M2.

As described above (refer to FIG. 8), each of the drive circuits 50generates a modulation signal obtained by the integrated circuit device500 pulse-modulating the input drive data dA (or dB) and generates anamplified control signal based on the modulation signal. Then, the firsttransistor M1 and the second transistor M2 generate an amplifiedmodulation signal obtained by amplifying the modulation signal based onthe amplified control signal. In the low pass filter 560 including theinductor L1, the amplified modulation signal is demodulated and a drivesignal is generated. That is, the integrated circuit device 500, thefirst transistor M1, the second transistor M2, and the inductor L1,which are included in the drive circuit 50, are provided such that thedrive data dA (or dB) is input from the short side 431 side and thedrive signal COM-A (COM-B) is output from the short side 432 side.

It is preferable that the same number of the drive circuits 50 thatoutput the drive signal COM-A and the drive circuits 50 that output thedrive signal COM-B be provided out of the plurality of drive circuits50. In addition, it is preferable that the drive circuits 50 outputtingthe drive signal COM-A and the drive circuits 50 outputting the drivesignal COM-B be alternately arranged along the short side 432 from thelong side 433 side to the long side 434 side.

As described above, the drive circuit substrate 420 in the firstembodiment converts the original drive differential signals dDSA anddDSB, which are input from the input unit 440 provided on the short side431 side via the cable 19 (FFC 192), to the drive data pieces dA and dBby means of the drive data receiving unit 330 (not illustrated), andgenerates the drive signals COM-A and COM-B by means of the drive signalgenerating unit 460 provided on the short side 432 side. Then, the drivesignals COM-A and COM-B are output from the output unit 450 provided onthe short side 431 side through, for example, a different wiring layerof the substrate 430.

Referring back to FIG. 16, the heat dissipating fin 470 (an example of a“radiator”) is provided on a surface that is different from a surface ofthe drive circuit substrate 420 on which the drive circuits 50 areprovided, and is provided at a position where the drive circuits 50 andat least a part of the heat dissipating fin overlap each other when thedrive circuit substrate 420 is seen in the direction z (an example of a“planar view”).

Specifically, the heat dissipating fin 470 is provided on the back sideof the drive circuit substrate 420, which is different from the frontside where the drive circuits 50 are provided, and is provided such thatthe drive circuits 50 and at least a part of the dissipating fin overlapeach other when seen in the direction z. At this time, it is preferablethat the heat dissipating fin 470 be provided at a position where thefirst transistors M1 and the second transistors M2 of the drive circuits50 and the heat dissipating fin overlap each other.

As described above (refer to FIG. 8), the drive signal COM-A (or COM-B)output from the drive circuit 50 is a signal obtained by the low passfilter 560 formed of the inductor L1 and the capacitor C1 smoothing outan amplified modulation signal at the connection point (terminal Sw)between the first transistor M1 and the second transistor M2. That is,when currents of the drive signals COM-A and COM-B output by the driveunit 30 increase, currents flowing in the first transistor M1, thesecond transistor M2, and the inductor L1 increase. For this reason,power loss in each of the first transistor M1, the second transistor M2,and the inductor L1 increases. That is the main cause of heat generationin the drive circuit 50.

In addition, surface-mount type transistors are often used as the firsttransistors M1 and the second transistors M2 of the drive circuits 50 inorder to miniaturize the drive circuits 50. Heat generated in the firsttransistors M1 and the second transistors M2 is dissipated to thesubstrate 430, for example, by a heat spreader.

Therefore, the heat dissipating fin 470 can efficiently dissipate heat,which is dissipated to the substrate 430 by the first transistors M1 andthe second transistors M2, by the heat dissipating fin 470 beingprovided at a position where the first transistors M1 and the secondtransistors M2 of the drive circuits 50 and the heat dissipating finoverlap each other. That is, according to the first embodiment, it ispossible for the heat dissipating fin 470 to efficiently dissipate heatof the first transistors M1 and the second transistors M2.

The heat dissipating fan 480 (an example of a “fan”) is provided at aposition intersecting a direction where a plane of the drive circuitsubstrate 420 extends. A distance between the heat dissipating fan 480and the drive circuit 50 is shorter than a distance between the heatdissipating fan 480 and the connector 441, and the distance between theheat dissipating fan 480 and the drive circuit 50 is shorter than adistance between the heat dissipating fan 480 and the connector 451.

Specifically, the heat dissipating fan 480 is provided on a drivecircuit 50 side of the drive circuit substrate 420. Accordingly, it ispossible for the heat dissipating fan 480 to efficiently cool the drivecircuits 50 and the first transistors M1, the second transistors M2, andthe inductors L1, which are mounted on the drive circuits 50. The heatdissipating fan 480 is provided so as to intersect a plane of thesubstrate 430 of the drive circuit substrate 420. Accordingly, it ispossible to dissipate heat of both of the front side and the back sideof the drive circuit substrate 420, and it is also possible tosimultaneously cool, for example, heat of the heat dissipating fin 470provided on the back side. Consequently, it is also possible toefficiently cool the first transistors M1 and the second transistors M2.

In the first embodiment, the drive circuits 50 are disposed on the shortside 432 side of the drive circuit substrate 420, and the input unit 440and the output unit 450 are disposed on the short side 431 side of thedrive circuit substrate 420. It is preferable that the heat dissipatingfan 480 be disposed on the short side 432 side of the drive circuitsubstrate 420. Accordingly, it is possible for air flow generated by theheat dissipating fan 480 to efficiently cool the drive circuits 50without being obstructed by the input unit 440 and the output unit 450.

The heat dissipating fan 480 may be provided on the drive circuit 50side of the drive circuit substrate 420, may be provided, for example,on the short side 432 side of the long side 433 illustrated in FIG. 17,or may be provided on the short side 432 side of the long side 434.

The case 410 (an example of a “drive circuit accommodating unit”) has anopening portion 411 (an example of an “opening”), and accommodates thedrive circuit substrate 420. In a state where the drive circuitsubstrate 420 is accommodated through the opening portion 411, adistance between the opening portion 411 and the drive circuit 50 isshorter than a distance between the opening portion 411 and theconnector 441, and the distance between the opening portion 411 and thedrive circuit 50 is shorter than a distance between the opening portion411 and the connector 451. That is, in a state where the drive circuitsubstrate 420 is accommodated, the opening portion 411 is provided on aside where the drive circuits 50 of the drive circuit substrate 420 aremounted.

It is possible to efficiently dissipate heat by providing the openingportion 411 on the drive circuit 50 side where much heat is generatedwithout the heat staying in the case 410.

In the first embodiment, the drive circuits 50 are disposed on the shortside 432 side of the drive circuit substrate 420, and the input unit 440and the output unit 450 are disposed on the short side 431 side of thedrive circuit substrate 420. It is preferable that the opening portion411 be disposed on the short side 432 side of the drive circuitsubstrate 420.

The opening portion 411 may be provided on the drive circuit 50 side ofthe drive circuit substrate 420, may be provided, for example, on theshort side 432 side of the long side 433, or may be provided on theshort side 432 side of the long side 434.

In the first embodiment, the drive circuit substrate 420 is accommodatedin a closed space formed of the opening portion 411 and the heatdissipating fan 480. Accordingly, it is possible for the drive unit 30to reduce sticking of ink droplets to the drive circuit substrate 420.The heat dissipating fin 470, the heat dissipating fan 480, and theopening portion 411 of the case 410 are provided on the side where thedrive circuits 50 of the drive circuit substrate 420 are mounted.Therefore, the drive circuits 50 are efficiently cooled by the heatdissipating fin 470, the heat dissipating fan 480, and the openingportion 411 of the case 410 without being obstructed by the input unit440 and the output unit 450. At this time, it is preferable to disposethe heat dissipating fan 480 such that heat generated inside the case410 of the liquid discharging apparatus 1 is discharged to the outsideof the liquid discharging apparatus 1. Accordingly, an effect of heat ona configuration other than the drive unit 30 can be reduced without heatgenerated in the drive unit 30 staying inside the liquid dischargingapparatus 1. The stay of air flow generated by the heat dissipating fan480 inside the liquid discharging apparatus 1 is reduced. Accordingly,it is possible for the liquid discharging apparatus 1 to perform stabledischarging.

As described above, an efficient cooling by various cooling members (forexample, the heat dissipating fan 480, the heat dissipating fin 470, andthe opening portion 411) is possible by separately disposing the inputunit 440 into which a signal is input, the output unit 450 from which asignal is output, and the drive signal generating unit 460, in whichheat is generated, on the drive circuit substrate 420 of the drive unit30 in the first embodiment. Therefore, according to the firstembodiment, the drive unit 30 and the drive circuit substrate 420, whichensure a high degree of freedom of disposing the various coolingmembers, can be realized.

1.6 Operational Advantages

In the liquid discharging apparatus 1 according to the first embodiment,the distance between the input unit 440 and the output unit 450 isshorter than the distance between both of the input unit 440 and theoutput unit 450 and the drive circuit 50, on the drive circuit substrate420 generating the drive signals COM-A and COM-B. That is, a regionwhere the input unit 440 and the output unit 450 are disposed and aregion where the drive circuits 50 generating heat are disposed aredisposed in different regions on the drive circuit substrate 420.Accordingly, it is possible to dispose a cooling component provided onthe drive circuits 50 generating heat without being restricted by theinput unit 440 which inputs signals into the drive circuit 50 and theoutput unit 450 which outputs signals from the drive circuits 50.Therefore, it is possible to provide the liquid discharging apparatus 1,in which restriction of disposing the cooling component is reduced and ahigh degree of freedom of disposing the cooling component is ensured.

It is possible to optimally dispose the cooling component on the drivecircuits 50, and it is possible to efficiently cool a heat generatingcomponent. It is possible to reduce an effect of heat generated in thedrive circuits 50 on a peripheral configuration and an effect ondischarge characteristics and the product life of the liquid dischargingapparatus 1 can be reduced.

In the liquid discharging apparatus 1 according to the first embodiment,the heat dissipating fan 480 is included as a cooling device and theheat dissipating fan 480 is provided on the side where the drivecircuits 50 are provided on the drive circuit substrate 420.Accordingly, it is possible for the heat dissipating fan 480 toefficiently cool the drive circuits 50 without being affected by thedisposition of the input unit 440 and the output unit 450.

In the liquid discharging apparatus 1 according to the first embodiment,the heat dissipating fan 480 is provided so as to intersect a directionwhere the plane of the drive circuit substrate 420 extends. That is, itis possible to selectively cool both of or one of the front side and theback side of the drive circuit substrate 420, and it is possible toefficiently cool the drive circuit substrate 420.

In the liquid discharging apparatus 1 according to the first embodiment,the drive circuit substrate 420 may be accommodated in the case 410having the opening portion 411. The sticking of a liquid discharged fromthe head 21 to the drive circuit substrate 420 is reduced by the case410 accommodating the drive circuit substrate 420. Therefore, on thedrive circuit substrate 420, the occurrence of a defect such as aninsulation failure caused by a liquid discharged from the head 21 isreduced.

In the liquid discharging apparatus 1 according to the first embodiment,the opening portion 411 of the case 410 is provided on the drive circuit50 side of the drive circuit substrate 420 so as to intersect thedirection where the plane of the drive circuit substrate 420 extends.That is, heat generated in the drive circuits 50 is discharged to theoutside of the case 410 from the opening portion 411, and thereby thestay of the heat inside the case 410 is reduced. Therefore, it ispossible to efficiently cool the drive circuits 50.

In the liquid discharging apparatus 1 according to the first embodiment,the heat dissipating fin 470 is included as a cooling device and theheat dissipating fin 470 is provided on a surface, which is differentfrom a surface of the drive circuit substrate 420 on which the drivecircuits 50 are provided, and is provided so as to overlap the drivecircuits 50. That is, the heat dissipating fin 470 dissipates heatgenerated in the drive circuits 50 from a surface of the drive circuitsubstrate 420 on which the drive circuits 50 are not provided.Accordingly, it is possible to efficiently dissipate heat generated inthe drive circuits 50.

As described above, it is possible to cool the drive circuits 50 byseparately disposing the input unit 440 into which a signal is input,the output unit 450 from which a signal is output, and the drive signalgenerating unit 460, in which heat is generated, on the drive circuitsubstrate 420 of the drive unit 30 in the first embodiment without thevarious cooling members (for example, the heat dissipating fan 480, theheat dissipating fin 470, and the opening portion 411) receiving effectsof the input unit 440 and the output unit 450. Therefore, it is possibleto realize the drive unit 30 and the drive circuit substrate 420, whichensure a high degree of freedom of disposing the various coolingmembers.

2 Second Embodiment

Although the liquid discharging apparatus 1 according to a secondembodiment has the same configuration as the liquid dischargingapparatus 1 according to the liquid discharging apparatus 1, the layoutof the drive signal generating unit 460 of the drive circuit substrate420 included in the drive unit 30 is different. Hereinafter, descriptionon the contents overlapping the first embodiment will be omitted orsimplified, and contents different from the first embodiment will bemainly described.

FIG. 18 is a schematic view illustrating the layout of the drive circuitsubstrate 420 according to the second embodiment. In FIG. 18, thedirection x, the direction y, and the direction z, which are orthogonalto each other, are illustrated and description will be given.

The liquid discharging apparatus 1 according to the second embodimenthas the same configuration as the liquid discharging apparatus 1according to the first embodiment, and illustration and descriptionthereof will be omitted (FIG. 1). The liquid discharging apparatus 1according to the second embodiment has the same electrical configurationas the first embodiment, and illustration and description thereof willbe omitted (FIG. 2). The configuration of the head 21, the configurationof a drive signal, and the operation of the drive circuits 50 of theliquid discharging apparatus 1 according to the second embodiment arethe same as in the first embodiment, and illustration and descriptionthereof will be omitted (FIGS. 3 to 13). In addition, the configurationof the printing unit 5 of the liquid discharging apparatus 1 accordingto the second embodiment is the same as in the first embodiment, andillustration and description thereof will be omitted (FIGS. 14 and 15).

As in the first embodiment, the drive unit 30 according to the secondembodiment is configured so as to include the case 410, the drivecircuit substrate 420, the heat dissipating fin 470, and the heatdissipating fan 480 (refer to FIG. 16).

FIG. 18 is a schematic view illustrating the layout of the drive circuitsubstrate 420 according to the second embodiment. The substrate 430 issubstantially rectangular, and is formed of the short side 431 and theshort side 432, which extend in the direction y and oppose each other,and the long side 433 and the long side 434, which extend in thedirection x and oppose each other.

As in the first embodiment, the input unit 440 is configured so as toinclude the plurality of (three in the second embodiment) connectors441, which are arranged along the long side 433 from the short side 431side to the short side 432 side. The cable 19 (FFC 192) is connected toeach of the plurality of connectors 441, and signals including theoriginal drive differential signals dDSA and dDSB and a power supplyvoltage for operating the drive unit 30 are input from the control unit10 into the each of the plurality of connectors.

As in the first embodiment, the output unit 450 is configured so as toinclude the plurality of (eight in the second embodiment) connectors451, which are arranged along the long side 434 from the short side 431side to the short side 432 side. The cable 19 (FFC 194) is connected toeach of the plurality of connectors 451, and signals including the drivesignals COM-A and COM-B and the voltage VBS are output to the head unit20.

The drive signal generating unit 460 is configured of a plurality of(four in the second embodiment) capacitors 461 and the plurality of(four in the second embodiment) drive circuits 50, and is provided nearthe short side 432 of the substrate 430.

The plurality of drive circuits 50 are arranged along the long side 434from the short side 432 side to the short side 431 side. The capacitor461 on the long side 433 side is provided for each of the plurality ofdrive circuits 50. The plurality of capacitors 461 are provided so as tocorrespond to the plurality of drive circuits 50 respectively, andstabilize a power, supply voltage supplied to each of the plurality ofdrive circuits 50.

As in the first embodiment, each of the drive circuits 50 is configuredso as to include the integrated circuit device 500, the first transistorM1, the second transistor M2, and the inductor L1.

The inductors L1 are provided on the long side 434 side of the drivecircuits 50. The first transistors M1 and the second transistors M2 arearranged in the direction x on the long side 433 side of the inductorsL1. In addition, the integrated circuit devices 500 are also provided onthe long side 433 side of the arranged first transistors M1 and thesecond transistors M2.

That is, the integrated circuit device 500, the first transistor M1, thesecond transistor M2, and the inductor L1, which are included in thedrive circuit 50, are provided such that the drive data dA (or dB) isinput from the long side 433 side and the drive signal COM-A (COM-B) isoutput to the long side 434 side.

As in the first embodiment, it is preferable that the same number of thedrive circuits 50 that output the drive signal COM-A and the drivecircuits 50 that output the drive signal COM-B be provided out of theplurality of drive circuits 50. In addition, it is preferable that thedrive circuits 50 outputting the drive signal COM-A and the drivecircuits 50 outputting the drive signal COM-B be alternately arrangedalong the long side 433 from the short side 432 side to the short side431.

As described above, in the drive circuit substrate 420 in the secondembodiment, the original drive differential signals dDSA and dDSB, whichare input from the input unit 440 provided on the short side 431 side ofthe long side 433 via the cable 19 (FFC 192), are input into the drivesignal generating unit 460 provided along the long side 433 on the shortside 432 side.

The original drive differential signals dDSA and dDSB input in the drivesignal generating unit 460 are converted to the drive data pieces dA anddB by the drive data receiving unit 330 (not illustrated), and the drivesignals COM-A and COM-B are generated by the drive signal generatingunit 460. Then, the drive signals COM-A and COM-B are output from theoutput unit 450 provided along the long side 434 on the short side 431side of the long side 434. That is, in the second embodiment, it ispossible to perform wiring such that the weak original drivedifferential signals dDSA and dDSB and the drive signals COM-A and COM-Bon the substrate 430 are not mixed with the original drive differentialsignals crossing the drive signals. Therefore, it is possible to reduceinterference between signals transmitted by the drive circuit substrate420.

Accordingly, it is possible for the drive unit 30 to improve a degree offreedom of disposing the cooling members for cooling withoutdeteriorating the accuracy of signals transmitted by the drive circuitsubstrate 420.

3 Modification Example

Although a piezoelectric liquid discharging apparatus in which a drivecircuit drives a piezoelectric element (capacitive load) as a drivingelement is given as an example in the embodiment described above, theinvention is also applicable to a liquid discharging apparatus in whicha drive circuit drives a driving element other than a capacitive load.As an example of such a liquid discharging apparatus, a thermal (bubbletype) liquid discharging apparatus, in which a drive circuit drives aheater element (for example, a resistance) as a driving element and aliquid is discharged using bubbles generated by the heater element beingheated, can be given.

Although a printing apparatus such as a printer is given as an exampleof a liquid discharging apparatus in the embodiments described above,the invention may be a liquid discharging apparatus that discharges aliquid onto a medium having a size of A3 or larger, and is alsoapplicable to liquid discharging apparatuses including a color materialdischarging apparatus used in manufacturing color filters, such as aliquid crystal display, an electrode material discharging apparatus usedin forming electrodes, such as an organic EL display and a fieldemission display (FED), a bioorganic material discharging apparatus usedin manufacturing biochips, a three-dimensional modelling apparatus(so-called 3D printer), and a textile printing apparatus.

Although the embodiments described above or the modification example hasbeen described, the invention is not limited to the embodiments or themodification example, and can be carried out in various forms withoutdeparting from the spirit of the invention. For example, the embodimentsand each modification example described above can be combined asappropriate.

The invention includes practically the same configuration (for example,a configuration of which a functions, a method, and a result are thesame or a configuration of which an object and an advantage are thesame) as the configuration described in the embodiments. The inventionincludes a configuration where an inessential portion of theconfiguration described in the embodiments is substituted. The inventionincludes a configuration with which the same operational advantagesdescribed in the embodiments are achieved or a configuration with whichthe same object can be accomplished. In addition, the invention includesa configuration where a known technique is added to the configurationdescribed in the embodiments.

The entire disclosure of Japanese Patent Application No. 2017-056643,filed Mar. 22, 2017 is expressly incorporated by reference herein.

What is claimed is:
 1. A liquid discharging apparatus comprising: aprint head that includes a driving element and discharges a liquid whena drive signal is applied and the driving element is driven; a drivesignal generation circuit that generates the drive signal based on adrive signal generation control signal for controlling generation of thedrive signal; and a drive circuit substrate on which the drive signalgeneration circuit is provided, the drive circuit substrate including aninput connector that is electrically connected with a first flexibleflat cable and inputs the drive signal generation control signal intothe drive circuit substrate, and an output connector that iselectrically connected with a second flexible flat cable which isdifferent from the first flexible flat cable and outputs the drivesignal generated by the drive signal generation circuit to the drivingelement, wherein a distance between the input connector and the outputconnector is shorter than both of a distance between the drive signalgeneration circuit and the input connector, and a distance between thedrive signal generation circuit and the output connector, a position ofthe input connector in a first direction does not overlap a position ofthe drive signal generation circuit in the first direction, a positionof the output connector in the first direction does not overlap theposition of the drive signal generation circuit in the first direction,a position of the input connector in a second direction which crossesthe first direction is different from a position of the output connectorin the second direction, and a position of the input connector in thefirst direction at least partly overlaps the position of the outputconnector in the first direction.
 2. The liquid discharging apparatusaccording to claim 1, further comprising: a fan, wherein the fan isprovided at a position intersecting an extending direction where a planeof the drive circuit substrate extends, a distance between the fan andthe drive signal generation circuit is shorter than a distance betweenthe fan and the input connector, and the distance between the fan andthe drive signal generation circuit is shorter than a distance betweenthe fan and the output connector.
 3. The liquid discharging apparatusaccording to claim 2, a longitudinal plane of the drive circuitsubstrate extends in a first direction, and the fan is provided along asecond direction which crosses the first direction.
 4. The liquiddischarging apparatus according to claim 1, further comprising: a drivecircuit accommodating unit that accommodates the drive circuit substrateand has an opening, wherein the opening is provided at a positionintersecting an extending direction where a plane of the drive circuitsubstrate extends, a distance between the opening and the drive signalgeneration circuit is shorter than a distance between the opening andthe input connector, and the distance between the opening and the drivesignal generation circuit is shorter than a distance between the openingand the output connector.
 5. The liquid discharging apparatus accordingto claim 1, further comprising: a radiator, the radiator is provided ona surface of the drive circuit substrate, which is different from asurface on which the drive signal generation circuit is provided, and inplanar view of the drive circuit substrate, the drive signal generationcircuit and the radiator are provided at positions where at least a partof the drive signal generation circuit and a part of the radiatoroverlap each other.
 6. The liquid discharging apparatus according toclaim 1, wherein the drive signal generation control signal is a digitalsignal, the drive signal generation circuit generates an underlyingdrive signal, which is an underlying analog signal of the drive signal,based on the drive signal generation control signal, and the drivesignal generation circuit power-amplifies the underlying drive signal togenerate the drive signal.
 7. The liquid discharging apparatus accordingto claim 1, wherein the drive circuit substrate includes a capacitor, atransistor and an inductor.
 8. The liquid discharging apparatusaccording to claim 1, wherein the first direction extends along a longside of the drive circuit substrate, and the second direction extendsalong a short side of the drive circuit substrate.
 9. The liquiddischarging apparatus according to claim 1, wherein the drive circuitsubstrate includes a plurality of input connectors including the inputconnector, and a plurality of output connectors including the outputconnector, a number of the input connectors is less than a number of theoutput connectors.
 10. The liquid discharging apparatus according toclaim 9, wherein the input connectors are aligned along the firstdirection, and the output connectors are aligned along the firstdirection.
 11. A circuit substrate comprising: an input connector thatis electrically connected with a first flexible flat cable; a drivesignal generation circuit that generates a drive signal for driving adriving element based on a drive signal generation control signalinputted through the input connector; and an output connector that iselectrically connected with a second flexible flat cable which isdifferent from the first flexible flat cable and outputs the drivesignal generated by the drive signal generation circuit to the drivingelement, wherein a distance between the input connector and the outputconnector is shorter than both of a distance between the drive signalgeneration circuit and the input connector, and a distance between thedrive signal generation circuit and the output connector, a position ofthe input connector in a first direction does not overlap a position ofthe drive signal generation circuit in the first direction, a positionof the output connector in the first direction does not overlap theposition of the drive signal generation circuit in the first direction,a position of the input connector in a second direction which crossesthe first direction is different from a position of the output connectorin the second direction, and a position of the input connector in thefirst direction at least partly overlaps the position of the outputconnector in the first direction.
 12. The circuit substrate according toclaim 11, wherein the position of the input connector in the firstdirection and the position of the output connector in the firstdirection are located on a same side with respect to the drive signalgeneration circuit.
 13. The circuit substrate according to claim 11,further comprising: a capacitor; a transistor; and an inductor.
 14. Theliquid discharging apparatus according to claim 11, wherein the firstdirection extends along a long side of the drive circuit substrate, andthe second direction extends along a short side of the drive circuitsubstrate.
 15. The liquid discharging apparatus according to claim 11,wherein the drive circuit substrate includes a plurality of inputconnectors including the input connector, and a plurality of outputconnectors including the output connector, a number of the inputconnectors is less than a number of the output connectors.
 16. Theliquid discharging apparatus according to claim 15, wherein the inputconnectors are aligned along the first direction, and the outputconnectors are aligned along the first direction.
 17. A liquiddischarging apparatus comprising: a print head that includes a drivingelement and discharges a liquid when a drive signal is applied and thedriving element is driven; a drive signal generation circuit thatgenerates the drive signal based on a drive signal generation controlsignal for controlling generation of the drive signal; a drive circuitsubstrate on which the drive signal generation circuit is provided; anda radiator, the drive circuit substrate including an input connectorthat inputs the drive signal generation control signal into the drivecircuit substrate, and an output connector that outputs the drive signalfrom the drive circuit substrate, a distance between the input connectorand the output connector being shorter than a distance between the drivesignal generation circuit and the input connector, the distance betweenthe input connector and the output connector being shorter than adistance between the drive signal generation circuit and the outputconnector, the radiator being provided on a surface of the drive circuitsubstrate, which is different from a surface on which the drive signalgeneration circuit is provided, and in planar view of the drive circuitsubstrate, the drive signal generation circuit and the radiator beingprovided at positions where at least a part of the drive signalgeneration circuit and a part of the radiator overlap each other.